graph4-cumulative-reported-cases-sierra-leone
graph分类的损失函数
graph分类的损失函数
在图分类任务中，损失函数的选择可以根据具体的问题和模型架构来决定。
以下是几种常见的图分类损失函数：
1. 交叉熵损失函数（Cross-Entropy Loss），交叉熵是一种常用的损失函数，用于衡量模型输出与真实标签之间的差异。
对于图分类任务，可以将图的标签视为一个概率分布，然后使用交叉熵损失函数来衡量模型输出的概率分布与真实标签之间的差异。
2. 对比损失函数（Contrastive Loss），对比损失函数用于学习图像或图表征的相似性。
在图分类中，可以使用对比损失函数来鼓励同一类别的图像或图表征在嵌入空间中更加接近，不同类别的图像或图表征在嵌入空间中更加远离。
3. 信息熵损失函数（Entropy Loss），信息熵损失函数用于衡量模型输出的不确定性。
在图分类任务中，可以使用信息熵损失函数来鼓励模型输出的概率分布更加均匀，从而增加模型对不同类别的区分能力。
4. 距离损失函数（Distance Loss），距离损失函数用于衡量
图像或图表征之间的距离。
在图分类中，可以使用距离损失函数来鼓励同一类别的图像或图表征之间的距离更小，不同类别的图像或图表征之间的距离更大。
5. 多标签损失函数（Multi-Label Loss），多标签损失函数适用于图分类任务中每个图可能具有多个标签的情况。
常见的多标签损失函数包括二元交叉熵损失函数、二元对数损失函数等，用于衡量每个标签的预测与真实标签之间的差异。
需要注意的是，在选择损失函数时，应根据具体任务的特点和数据集的属性进行合理选择，并结合模型的架构和优化目标进行综合考虑。
Tektronix MDO3000 Series 数字多功能作业仪用户指南说明书
19StandardMath ToolsDisplay up to four math function traces (F1-F4). The easy-to-use graphical interface simplifies setup of up to two operations on each function trace;and function traces can be chained together to perform math-on-math.absolute value integralaverage (summed)invert (negate)average (continuous)log (base e)custom (MATLAB) – limited points product (x)derivativeratio (/)deskew (resample)reciprocaldifference (–)rescale (with units)enhanced resolution (to 11 bits vertical)roof envelope (sinx)/x exp (base e)square exp (base 10)square root fft (power spectrum, magnitude, phase,sum (+)up to 50 kpts) trend (datalog) of 1000 events floorzoom (identity)histogram of 1000 eventsMeasure ToolsDisplay any 6 parameters together with statistics, including their average,high, low, and standard deviations. Histicons provide a fast, dynamic view of parameters and wave-shape characteristics.Pass/Fail TestingSimultaneously test multiple parameters against selectable parameter limits or pre-defined masks. Pass or fail conditions can initiate actions including document to local or networked files, e-mail the image of the failure, save waveforms, send a pulse out at the rear panel auxiliary BNC output, or (with the GPIB option) send a GPIB SRQ.Jitter and Timing Analysis Software Package (WRXi-JTA2)(Standard with MXi-A model oscilloscopes)•Jitter and timing parameters, with “Track”graphs of •Edge@lv parameter (counts edges)• Persistence histogram, persistence trace (mean, range, sigma)Software Options –Advanced Math and WaveShape AnalysisStatistics Package (WRXi-STAT)This package provides additional capability to statistically display measurement information and to analyze results:• Histograms expanded with 19 histogram parameters/up to 2 billion events.• Persistence Histogram• Persistence Trace (mean, range, sigma)Master Analysis Software Package (WRXi-XMAP)(Standard with MXi-A model oscilloscopes)This package provides maximum capability and flexibility, and includes all the functionality present in XMATH, XDEV, and JTA2.Advanced Math Software Package (WRXi-XMATH)(Standard with MXi-A model oscilloscopes)This package provides a comprehensive set of WaveShape Analysis tools providing insight into the wave shape of complex signals. Includes:•Parameter math – add, subtract, multiply, or divide two different parameters.Invert a parameter and rescale parameter values.•Histograms expanded with 19 histogram parameters/up to 2 billion events.•Trend (datalog) of up to 1 million events•Track graphs of any measurement parameter•FFT capability includes: power averaging, power density, real and imaginary components, frequency domain parameters, and FFT on up to 24 Mpts.•Narrow-band power measurements •Auto-correlation function •Sparse function• Cubic interpolation functionAdvanced Customization Software Package (WRXi-XDEV)(Standard with MXi-A model oscilloscopes)This package provides a set of tools to modify the scope and customize it to meet your unique needs. Additional capability provided by XDEV includes:•Creation of your own measurement parameter or math function, using third-party software packages, and display of the result in the scope. Supported third-party software packages include:– VBScript – MATLAB – Excel•CustomDSO – create your own user interface in a scope dialog box.• Addition of macro keys to run VBScript files •Support for plug-insValue Analysis Software Package (WRXi-XVAP)(Standard with MXi-A model oscilloscopes)Measurements:•Jitter and Timing parameters (period@level,width@level, edge@level,duty@level, time interval error@level, frequency@level, half period, setup, skew, Δ period@level, Δ width@level).Math:•Persistence histogram •Persistence trace (mean, sigma, range)•1 Mpts FFTs with power spectrum density, power averaging, real, imaginary, and real+imaginary settings)Statistical and Graphical Analysis•1 Mpts Trends and Histograms •19 histogram parameters •Track graphs of any measurement parameterIntermediate Math Software Package (WRXi-XWAV)Math:•1 Mpts FFTs with power spectrum density, power averaging, real, and imaginary componentsStatistical and Graphical Analysis •1 Mpts Trends and Histograms •19 histogram parameters•Track graphs of any measurement parameteramplitude area base cyclescustom (MATLAB,VBScript) –limited points delay Δdelay duration duty cyclefalltime (90–10%, 80–20%, @ level)firstfrequency lastlevel @ x maximum mean median minimumnumber of points +overshoot –overshoot peak-to-peak period phaserisetime (10–90%, 20–80%, @ level)rmsstd. deviation time @ level topΔ time @ levelΔ time @ level from triggerwidth (positive + negative)x@ max.x@ min.– Cycle-Cycle Jitter – N-Cycle– N-Cycle with start selection – Frequency– Period – Half Period – Width– Time Interval Error – Setup– Hold – Skew– Duty Cycle– Duty Cycle Error20WaveRunner WaveRunner WaveRunner WaveRunner WaveRunner 44Xi-A64Xi-A62Xi-A104Xi-A204Xi-AVertical System44MXi-A64MXi-A104MXi-A204MXi-ANominal Analog Bandwidth 400 MHz600 MHz600 MHz 1 GHz 2 GHz@ 50 Ω, 10 mV–1 V/divRise Time (Typical)875 ps500 ps500 ps300 ps180 psInput Channels44244Bandwidth Limiters20 MHz; 200 MHzInput Impedance 1 MΩ||16 pF or 50 Ω 1 MΩ||20 pF or 50 ΩInput Coupling50 Ω: DC, 1 MΩ: AC, DC, GNDMaximum Input Voltage50 Ω: 5 V rms, 1 MΩ: 400 V max.50 Ω: 5 V rms, 1 MΩ: 250 V max.(DC + Peak AC ≤ 5 kHz)(DC + Peak AC ≤ 10 kHz)Vertical Resolution8 bits; up to 11 with enhanced resolution (ERES)Sensitivity50 Ω: 2 mV/div–1 V/div fully variable; 1 MΩ: 2 mV–10 V/div fully variableDC Gain Accuracy±1.0% of full scale (typical); ±1.5% of full scale, ≥ 10 mV/div (warranted)Offset Range50 Ω: ±1 V @ 2–98 mV/div, ±10 V @ 100 mV/div–1 V/div; 50Ω:±400mV@2–4.95mV/div,±1V@5–99mv/div,1 M Ω: ±1 V @ 2–98 mV/div, ±10 V @ 100 mV/div–1 V/div,±10 V @ 100 mV–1 V/div±**********/div–10V/div 1 M Ω: ±400 mV @ 2–4.95 mV/div, ±1 V @5–99 mV/div, ±10 V @ 100 mV–1 V/div,±*********–10V/divInput Connector ProBus/BNCTimebase SystemTimebases Internal timebase common to all input channels; an external clock may be applied at the auxiliary inputTime/Division Range Real time: 200 ps/div–10 s/div, RIS mode: 200 ps/div to 10 ns/div, Roll mode: up to 1,000 s/divClock Accuracy≤ 5 ppm @ 25 °C (typical) (≤ 10 ppm @ 5–40 °C)Sample Rate and Delay Time Accuracy Equal to Clock AccuracyChannel to Channel Deskew Range±9 x time/div setting, 100 ms max., each channelExternal Sample Clock DC to 600 MHz; (DC to 1 GHz for 104Xi-A/104MXi-A and 204Xi-A/204MXi-A) 50 Ω, (limited BW in 1 MΩ),BNC input, limited to 2 Ch operation (1 Ch in 62Xi-A), (minimum rise time and amplitude requirements applyat low frequencies)Roll Mode User selectable at ≥ 500 ms/div and ≤100 kS/s44Xi-A64Xi-A62Xi-A104Xi-A204Xi-A Acquisition System44MXi-A64MXi-A104MXi-A204MXi-ASingle-Shot Sample Rate/Ch 5 GS/sInterleaved Sample Rate (2 Ch) 5 GS/s10 GS/s10 GS/s10 GS/s10 GS/sRandom Interleaved Sampling (RIS)200 GS/sRIS Mode User selectable from 200 ps/div to 10 ns/div User selectable from 100 ps/div to 10 ns/div Trigger Rate (Maximum) 1,250,000 waveforms/secondSequence Time Stamp Resolution 1 nsMinimum Time Between 800 nsSequential SegmentsAcquisition Memory Options Max. Acquisition Points (4 Ch/2 Ch, 2 Ch/1 Ch in 62Xi-A)Segments (Sequence Mode)Standard12.5M/25M10,00044Xi-A64Xi-A62Xi-A104Xi-A204Xi-A Acquisition Processing44MXi-A64MXi-A104MXi-A204MXi-ATime Resolution (min, Single-shot)200 ps (5 GS/s)100 ps (10 GS/s)100 ps (10 GS/s)100 ps (10 GS/s)100 ps (10 GS/s) Averaging Summed and continuous averaging to 1 million sweepsERES From 8.5 to 11 bits vertical resolutionEnvelope (Extrema)Envelope, floor, or roof for up to 1 million sweepsInterpolation Linear or (Sinx)/xTrigger SystemTrigger Modes Normal, Auto, Single, StopSources Any input channel, External, Ext/10, or Line; slope and level unique to each source, except LineTrigger Coupling DC, AC (typically 7.5 Hz), HF Reject, LF RejectPre-trigger Delay 0–100% of memory size (adjustable in 1% increments, or 100 ns)Post-trigger Delay Up to 10,000 divisions in real time mode, limited at slower time/div settings in roll modeHold-off 1 ns to 20 s or 1 to 1,000,000,000 events21WaveRunner WaveRunner WaveRunner WaveRunner WaveRunner 44Xi-A 64Xi-A 62Xi-A104Xi-A 204Xi-A Trigger System (cont’d)44MXi-A64MXi-A104MXi-A204MXi-AInternal Trigger Level Range ±4.1 div from center (typical)Trigger and Interpolator Jitter≤ 3 ps rms (typical)Trigger Sensitivity with Edge Trigger 2 div @ < 400 MHz 2 div @ < 600 MHz 2 div @ < 600 MHz 2 div @ < 1 GHz 2 div @ < 2 GHz (Ch 1–4 + external, DC, AC, and 1 div @ < 200 MHz 1 div @ < 200 MHz 1 div @ < 200 MHz 1 div @ < 200 MHz 1 div @ < 200 MHz LFrej coupling)Max. Trigger Frequency with400 MHz 600 MHz 600 MHz 1 GHz2 GHzSMART Trigger™ (Ch 1–4 + external)@ ≥ 10 mV@ ≥ 10 mV@ ≥ 10 mV@ ≥ 10 mV@ ≥ 10 mVExternal Trigger RangeEXT/10 ±4 V; EXT ±400 mVBasic TriggersEdgeTriggers when signal meets slope (positive, negative, either, or Window) and level conditionTV-Composite VideoT riggers NTSC or PAL with selectable line and field; HDTV (720p, 1080i, 1080p) with selectable frame rate (50 or 60 Hz)and Line; or CUSTOM with selectable Fields (1–8), Lines (up to 2000), Frame Rates (25, 30, 50, or 60 Hz), Interlacing (1:1, 2:1, 4:1, 8:1), or Synch Pulse Slope (Positive or Negative)SMART TriggersState or Edge Qualified Triggers on any input source only if a defined state or edge occurred on another input source.Delay between sources is selectable by time or eventsQualified First In Sequence acquisition mode, triggers repeatedly on event B only if a defined pattern, state, or edge (event A) is satisfied in the first segment of the acquisition. Delay between sources is selectable by time or events Dropout Triggers if signal drops out for longer than selected time between 1 ns and 20 s.PatternLogic combination (AND, NAND, OR, NOR) of 5 inputs (4 channels and external trigger input – 2 Ch+EXT on WaveRunner 62Xi-A). Each source can be high, low, or don’t care. The High and Low level can be selected independently. Triggers at start or end of the patternSMART Triggers with Exclusion TechnologyGlitch and Pulse Width Triggers on positive or negative glitches with widths selectable from 500 ps to 20 s or on intermittent faults (subject to bandwidth limit of oscilloscope)Signal or Pattern IntervalTriggers on intervals selectable between 1 ns and 20 sTimeout (State/Edge Qualified)Triggers on any source if a given state (or transition edge) has occurred on another source.Delay between sources is 1 ns to 20 s, or 1 to 99,999,999 eventsRuntTrigger on positive or negative runts defined by two voltage limits and two time limits. Select between 1 ns and 20 sSlew RateTrigger on edge rates. Select limits for dV, dt, and slope. Select edge limits between 1 ns and 20 s Exclusion TriggeringTrigger on intermittent faults by specifying the normal width or periodLeCroy WaveStream Fast Viewing ModeIntensity256 Intensity Levels, 1–100% adjustable via front panel control Number of Channels up to 4 simultaneouslyMax Sampling Rate5 GS/s (10 GS/s for WR 62Xi-A, 64Xi-A/64MXi-A,104Xi-A/104MXi-A, 204Xi-A/204MXi-A in interleaved mode)Waveforms/second (continuous)Up to 20,000 waveforms/secondOperationFront panel toggle between normal real-time mode and LeCroy WaveStream Fast Viewing modeAutomatic SetupAuto SetupAutomatically sets timebase, trigger, and sensitivity to display a wide range of repetitive signalsVertical Find ScaleAutomatically sets the vertical sensitivity and offset for the selected channels to display a waveform with maximum dynamic range44Xi-A 64Xi-A 62Xi-A104Xi-A 204Xi-A Probes44MXi-A 64MXi-A104MXi-A 204MXi-AProbesOne Passive probe per channel; Optional passive and active probes available Probe System; ProBus Automatically detects and supports a variety of compatible probes Scale FactorsAutomatically or manually selected, depending on probe usedColor Waveform DisplayTypeColor 10.4" flat-panel TFT-LCD with high resolution touch screenResolutionSVGA; 800 x 600 pixels; maximum external monitor output resolution of 2048 x 1536 pixelsNumber of Traces Display a maximum of 8 traces. Simultaneously display channel, zoom, memory, and math traces Grid StylesAuto, Single, Dual, Quad, Octal, XY , Single + XY , Dual + XY Waveform StylesSample dots joined or dots only in real-time mode22Zoom Expansion TracesDisplay up to 4 Zoom/Math traces with 16 bits/data pointInternal Waveform MemoryM1, M2, M3, M4 Internal Waveform Memory (store full-length waveform with 16 bits/data point) or store to any number of files limited only by data storage mediaSetup StorageFront Panel and Instrument StatusStore to the internal hard drive, over the network, or to a USB-connected peripheral deviceInterfaceRemote ControlVia Windows Automation, or via LeCroy Remote Command Set Network Communication Standard VXI-11 or VICP , LXI Class C Compliant GPIB Port (Accessory)Supports IEEE – 488.2Ethernet Port 10/100/1000Base-T Ethernet interface (RJ-45 connector)USB Ports5 USB 2.0 ports (one on front of instrument) supports Windows-compatible devices External Monitor Port Standard 15-pin D-Type SVGA-compatible DB-15; connect a second monitor to use extended desktop display mode with XGA resolution Serial PortDB-9 RS-232 port (not for remote oscilloscope control)44Xi-A 64Xi-A 62Xi-A104Xi-A 204Xi-A Auxiliary Input44MXi-A 64MXi-A104MXi-A 204MXi-ASignal Types Selected from External Trigger or External Clock input on front panel Coupling50 Ω: DC, 1 M Ω: AC, DC, GND Maximum Input Voltage50 Ω: 5 V rms , 1 M Ω: 400 V max.50 Ω: 5 V rms , 1 M Ω: 250 V max. (DC + Peak AC ≤ 5 kHz)(DC + Peak AC ≤ 10 kHz)Auxiliary OutputSignal TypeTrigger Enabled, Trigger Output. Pass/Fail, or Off Output Level TTL, ≈3.3 VConnector TypeBNC, located on rear panelGeneralAuto Calibration Ensures specified DC and timing accuracy is maintained for 1 year minimumCalibratorOutput available on front panel connector provides a variety of signals for probe calibration and compensationPower Requirements90–264 V rms at 50/60 Hz; 115 V rms (±10%) at 400 Hz, Automatic AC Voltage SelectionInstallation Category: 300 V CAT II; Max. Power Consumption: 340 VA/340 W; 290 VA/290 W for WaveRunner 62Xi-AEnvironmentalTemperature: Operating+5 °C to +40 °C Temperature: Non-Operating -20 °C to +60 °CHumidity: Operating Maximum relative humidity 80% for temperatures up to 31 °C decreasing linearly to 50% relative humidity at 40 °CHumidity: Non-Operating 5% to 95% RH (non-condensing) as tested per MIL-PRF-28800F Altitude: OperatingUp to 3,048 m (10,000 ft.) @ ≤ 25 °C Altitude: Non-OperatingUp to 12,190 m (40,000 ft.)PhysicalDimensions (HWD)260 mm x 340 mm x 152 mm Excluding accessories and projections (10.25" x 13.4" x 6")Net Weight7.26kg. (16.0lbs.)CertificationsCE Compliant, UL and cUL listed; Conforms to EN 61326, EN 61010-1, UL 61010-1 2nd Edition, and CSA C22.2 No. 61010-1-04Warranty and Service3-year warranty; calibration recommended annually. Optional service programs include extended warranty, upgrades, calibration, and customization services23Product DescriptionProduct CodeWaveRunner Xi-A Series Oscilloscopes2 GHz, 4 Ch, 5 GS/s, 12.5 Mpts/ChWaveRunner 204Xi-A(10 GS/s, 25 Mpts/Ch in interleaved mode)with 10.4" Color Touch Screen Display 1 GHz, 4 Ch, 5 GS/s, 12.5 Mpts/ChWaveRunner 104Xi-A(10 GS/s, 25 Mpts/Ch in interleaved mode)with 10.4" Color Touch Screen Display 600 MHz, 4 Ch, 5 GS/s, 12.5 Mpts/Ch WaveRunner 64Xi-A(10 GS/s, 25 Mpts/Ch in interleaved mode)with 10.4" Color Touch Screen Display 600 MHz, 2 Ch, 5 GS/s, 12.5 Mpts/Ch WaveRunner 62Xi-A(10 GS/s, 25 Mpts/Ch in interleaved mode)with 10.4" Color Touch Screen Display 400 MHz, 4 Ch, 5 GS/s, 12.5 Mpts/Ch WaveRunner 44Xi-A(25 Mpts/Ch in interleaved mode)with 10.4" Color Touch Screen DisplayWaveRunner MXi-A Series Oscilloscopes2 GHz, 4 Ch, 5 GS/s, 12.5 Mpts/ChWaveRunner 204MXi-A(10 GS/s, 25 Mpts/Ch in Interleaved Mode)with 10.4" Color Touch Screen Display 1 GHz, 4 Ch, 5 GS/s, 12.5 Mpts/ChWaveRunner 104MXi-A(10 GS/s, 25 Mpts/Ch in Interleaved Mode)with 10.4" Color Touch Screen Display 600 MHz, 4 Ch, 5 GS/s, 12.5 Mpts/Ch WaveRunner 64MXi-A(10 GS/s, 25 Mpts/Ch in Interleaved Mode)with 10.4" Color Touch Screen Display 400 MHz, 4 Ch, 5 GS/s, 12.5 Mpts/Ch WaveRunner 44MXi-A(25 Mpts/Ch in Interleaved Mode)with 10.4" Color Touch Screen DisplayIncluded with Standard Configuration÷10, 500 MHz, 10 M Ω Passive Probe (Total of 1 Per Channel)Standard Ports; 10/100/1000Base-T Ethernet, USB 2.0 (5), SVGA Video out, Audio in/out, RS-232Optical 3-button Wheel Mouse – USB 2.0Protective Front Cover Accessory PouchGetting Started Manual Quick Reference GuideAnti-virus Software (Trial Version)Commercial NIST Traceable Calibration with Certificate 3-year WarrantyGeneral Purpose Software OptionsStatistics Software Package WRXi-STAT Master Analysis Software Package WRXi-XMAP (Standard with MXi-A model oscilloscopes)Advanced Math Software Package WRXi-XMATH (Standard with MXi-A model oscilloscopes)Intermediate Math Software Package WRXi-XWAV (Standard with MXi-A model oscilloscopes)Value Analysis Software Package (Includes XWAV and JTA2) WRXi-XVAP (Standard with MXi-A model oscilloscopes)Advanced Customization Software Package WRXi-XDEV (Standard with MXi-A model oscilloscopes)Spectrum Analyzer and Advanced FFT Option WRXi-SPECTRUM Processing Web Editor Software Package WRXi-XWEBProduct Description Product CodeApplication Specific Software OptionsJitter and Timing Analysis Software Package WRXi-JTA2(Standard with MXi-A model oscilloscopes)Digital Filter Software PackageWRXi-DFP2Disk Drive Measurement Software Package WRXi-DDM2PowerMeasure Analysis Software Package WRXi-PMA2Serial Data Mask Software PackageWRXi-SDM QualiPHY Enabled Ethernet Software Option QPHY-ENET*QualiPHY Enabled USB 2.0 Software Option QPHY-USB †EMC Pulse Parameter Software Package WRXi-EMC Electrical Telecom Mask Test PackageET-PMT* TF-ENET-B required. †TF-USB-B required.Serial Data OptionsI 2C Trigger and Decode Option WRXi-I2Cbus TD SPI Trigger and Decode Option WRXi-SPIbus TD UART and RS-232 Trigger and Decode Option WRXi-UART-RS232bus TD LIN Trigger and Decode Option WRXi-LINbus TD CANbus TD Trigger and Decode Option CANbus TD CANbus TDM Trigger, Decode, and Measure/Graph Option CANbus TDM FlexRay Trigger and Decode Option WRXi-FlexRaybus TD FlexRay Trigger and Decode Physical Layer WRXi-FlexRaybus TDP Test OptionAudiobus Trigger and Decode Option WRXi-Audiobus TDfor I 2S , LJ, RJ, and TDMAudiobus Trigger, Decode, and Graph Option WRXi-Audiobus TDGfor I 2S LJ, RJ, and TDMMIL-STD-1553 Trigger and Decode Option WRXi-1553 TDA variety of Vehicle Bus Analyzers based on the WaveRunner Xi-A platform are available.These units are equipped with a Symbolic CAN trigger and decode.Mixed Signal Oscilloscope Options500 MHz, 18 Ch, 2 GS/s, 50 Mpts/Ch MS-500Mixed Signal Oscilloscope Option 250 MHz, 36 Ch, 1 GS/s, 25 Mpts/ChMS-500-36(500 MHz, 18 Ch, 2 GS/s, 50 Mpts/Ch Interleaved) Mixed Signal Oscilloscope Option 250 MHz, 18 Ch, 1 GS/s, 10 Mpts/Ch MS-250Mixed Signal Oscilloscope OptionProbes and Amplifiers*Set of 4 ZS1500, 1.5 GHz, 0.9 pF , 1 M ΩZS1500-QUADPAK High Impedance Active ProbeSet of 4 ZS1000, 1 GHz, 0.9 pF , 1 M ΩZS1000-QUADPAK High Impedance Active Probe 2.5 GHz, 0.7 pF Active Probe HFP25001 GHz Active Differential Probe (÷1, ÷10, ÷20)AP034500 MHz Active Differential Probe (x10, ÷1, ÷10, ÷100)AP03330 A; 100 MHz Current Probe – AC/DC; 30 A rms ; 50 A rms Pulse CP03130 A; 50 MHz Current Probe – AC/DC; 30 A rms ; 50 A rms Pulse CP03030 A; 50 MHz Current Probe – AC/DC; 30 A rms ; 50 A peak Pulse AP015150 A; 10 MHz Current Probe – AC/DC; 150 A rms ; 500 A peak Pulse CP150500 A; 2 MHz Current Probe – AC/DC; 500 A rms ; 700 A peak Pulse CP5001,400 V, 100 MHz High-Voltage Differential Probe ADP3051,400 V, 20 MHz High-Voltage Differential Probe ADP3001 Ch, 100 MHz Differential Amplifier DA1855A*A wide variety of other passive, active, and differential probes are also available.Consult LeCroy for more information.Product Description Product CodeHardware Accessories*10/100/1000Base-T Compliance Test Fixture TF-ENET-B †USB 2.0 Compliance Test Fixture TF-USB-B External GPIB Interface WS-GPIBSoft Carrying Case WRXi-SOFTCASE Hard Transit CaseWRXi-HARDCASE Mounting Stand – Desktop Clamp Style WRXi-MS-CLAMPRackmount Kit WRXi-RACK Mini KeyboardWRXi-KYBD Removable Hard Drive Package (Includes removeable WRXi-A-RHD hard drive kit and two hard drives)Additional Removable Hard DriveWRXi-A-RHD-02* A variety of local language front panel overlays are also available .† Includes ENET-2CAB-SMA018 and ENET-2ADA-BNCSMA.Customer ServiceLeCroy oscilloscopes and probes are designed, built, and tested to ensure high reliability. In the unlikely event you experience difficulties, our digital oscilloscopes are fully warranted for three years, and our probes are warranted for one year.This warranty includes:• No charge for return shipping • Long-term 7-year support• Upgrade to latest software at no chargeLocal sales offices are located throughout the world. Visit our website to find the most convenient location.© 2010 by LeCroy Corporation. All rights reserved. Specifications, prices, availability, and delivery subject to change without notice. Product or brand names are trademarks or requested trademarks of their respective holders.1-800-5-LeCroy WRXi-ADS-14Apr10PDF。
四参数拟合曲线标准
四参数拟合曲线标准===========四参数拟合曲线是一种广泛应用于各种科学和工程领域的曲线拟合方法。
这种方法通过四个参数来描述数据的分布和趋势，具有较高的灵活性和适用性。
本篇文档将详细介绍四参数拟合曲线的标准，包括参数定义、参数约束、拟合度评估、误差分析、曲线形状和应用场景等方面。
1. 参数定义-------四参数拟合曲线由四个参数定义，它们分别是：* a：曲线的垂直偏移量，决定了曲线在y轴上的位置；* b：曲线的水平宽度，决定了曲线在x轴上的分布范围；* c：曲线的斜率，反映了曲线在某一特定x值上y值的增加或减少速率；* d：曲线的形状因子，决定了曲线的弯曲程度。
这四个参数可以通过最小二乘法等数学方法进行求解，使得拟合曲线与实际数据之间达到最佳的匹配效果。
2. 参数约束-------在四参数拟合曲线的求解过程中，需要对参数进行一些约束。
这些约束条件可以保证求解的参数值具有物理意义和实际应用价值。
常见的参数约束包括：* a, b, c, d均为非负值；* a, b, c, d的取值应保证拟合曲线的平滑性和连续性；* 对称性：对于某些特定的数据集，拟合曲线可能呈现出对称性，此时应约束c和d的取值。
这些约束条件的设立可以帮助我们更好地理解数据集的本质特征，避免不合理的参数值组合对拟合结果产生负面影响。
3. 拟合度评估-------为了衡量四参数拟合曲线的效果，需要对拟合度进行评估。
常用的评估方法包括：均方根误差(RMSE)、平均绝对误差(MAE)、R-squared值等。
这些评估指标可以定量地描述拟合曲线与实际数据之间的差异程度，从而判断四参数拟合曲线的拟合效果。
一般来说，RMSE值越小，MAE值越小，R-squared值越接近1，说明拟合效果越好。
4. 误差分析-------除了对拟合度进行评估外，还需要对误差进行分析。
误差主要包括系统误差和随机误差。
系统误差是由模型本身的不完善、测量设备误差等因素引起的；随机误差是由偶然的、难以控制的因素引起的。
kmeans聚类算法检测故障的matlab程序 -回复
kmeans聚类算法检测故障的matlab程序-回复k-means聚类算法是一种常用的数据分析方法，它通过将数据集划分为多个独立的聚类，来发现数据中的隐含结构。
在故障检测领域，k-means聚类算法也可以应用于故障诊断和故障预测领域。
本文将详细介绍基于k-means聚类算法的故障检测Matlab程序的步骤和实现。
首先，我们需要明确故障检测的目标。
在工业生产中，设备故障会导致生产过程中的异常情况，可能造成生产效率下降甚至事故发生。
因此，通过检测故障并及时采取措施可以提高生产效率和产品质量。
在这个基础上，我们可以利用k-means聚类算法对采集到的数据进行故障检测。
接下来，我们将详细介绍k-means聚类算法的步骤及其在故障检测中的应用。
1. 数据准备：在开始之前，我们需要采集并准备好与故障相关的数据。
这些数据可以包括设备的传感器读数、设备参数等。
为了保证算法的准确性，需要确保数据的质量和完整性。
2. 设置聚类数目：通过k-means聚类算法，我们将数据集划分为k个聚类。
在故障检测中，聚类的数目通常是根据实际情况和需求来确定的。
过少的聚类数目可能会导致故障检测不准确，而过多的聚类数目则会增加计算复杂度。
3. 特征提取：对于数据集中的每个样本，我们需要提取适当的特征，以便进行聚类分析。
特征提取的目的是将样本从高维空间映射到低维空间，从而减少计算复杂度和噪声的影响。
通常，特征选择可以基于统计学指标、主成分分析等方法来进行。
4. 标准化：在聚类算法中，我们还需要对特征进行标准化，以确保每个特征的重要性相等。
常见的标准化方法包括z-score归一化和min-max归一化等。
标准化后的数据可以使得聚类算法更加准确和稳定。
5. 聚类分析：在进行聚类分析之前，我们需要选择合适的距离度量方法。
常见的距离度量方法有欧氏距离、曼哈顿距离等。
然后，我们可以利用k-means算法对准备好的数据进行聚类分析，并得到每个样本所属的聚类簇。
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BTBU_4.2 Audit Partner Specialization and Audit Fees_ Some Evidence from Sweden
Audit Partner Specialization and Audit Fees:Some Evidencefrom Sweden*MIKKO ZERNI,University of Vaasa1.IntroductionThe purpose of this study is to examine auditor specialization and pricing at the individual partner level.1In the aftermath of major accounting scandals such as ComROAD AG, Enron,Parmalat,Tyco,Waste Management,and WorldCom,regulators and investment communities have been seeking to restore investor confidence in the capital markets.The response worldwide has been increases in regulation,and in these reforms accounting and auditing have been identified as priority areas to‘‘fix’’.For instance,with the aim of increasing audit market transparency,the amended European Union’s(EU’s)8th Directive requires the disclosure of engagement partner identity.2Currently,the Public Company Accounting Oversight Board(PCAOB)in the United States is considering a similar requirement.On October6,2008,the U.S.Treasury’s Advisory Committee on the Audit-ing Profession(ACAP)issued itsfinal report,which recommends,among other things,‘‘urging the PCAOB to undertake a standard-setting initiative to consider mandating the engagement partner’s signature on the auditor’s report’’(ACAP Report,October6,2008, at VII:19).3According to the ACAP’s recommendation,the requirement for the engage-ment partner to sign the audit report could improve audit quality in two ways:‘‘First,it might increase the engagement partner’s sense of accountability tofinancial statement *Accepted by Ferdinand A.Gul.An earlier draft of this paper was entitled‘‘Audit Partner Specialization, Audit Fees,and Auditor-Client Alignments’’.I appreciate the comments received from Ferdinand A.Gul (the associate editor),two anonymous reviewers,Pekka Alatalo(KPMG Finland),Jean C.Bedard(discus-sant),Andy Conlin,Ann Gaeremynck,Kaarina Halonen(PWC Finland),Seppo Ika heimo,Henry Jarva, Juha Joenva a ra,Juha-Pekka Kallunki,Eija Kangas(KPMG Finland),Robert Knechel,Anna-Maija Lantto, Christophe Van Linden,Lasse Niemi,Henrik Nilsson,Mervi Niskanen,Jukka Perttunen,Peter Pope, Markku Rahiala,Veijo Riistama(PWC Finland),Petri Sahlstro m,Stefan Sundgren,Risto Tuppurainen, Sofie Vandenbogaerde,Ann Vanstraelen,Markku Vieru,Marleen Willekens,and Erik A stro m(Ernst& Young Sweden).I would also like to thank the participants at the24th Contemporary Accounting Research Conference in Montreal Canada(2009),AFI seminar at Katholieke Universiteit Leuven(2011)and the AFAR workshop in Vaasa(2008)for their comments.I wish to thank Tuomas Anttila,Marja Kauppinen, and Harri Lempola for their excellent research assistance.Financial support received from the NASDAQ OMX Nordic Foundation,the Finnish Foundation for the Advancement of Securities Markets,the Founda-tion for Economic Education,the Ostrobothnia Cultural Foundation,and the Finnish Cultural Foundation is gratefully acknowledged.This research is part of research projects by the Academy of Finland(Grant Numbers140000and126630).All remaining errors are mine alone.1.The terms‘‘auditor specialization’’and‘‘auditor expertise’’,as well as the terms‘‘engagement partner’’,‘‘auditor’’,and‘‘audit partner in charge’’are used interchangeably in this study.2.The new EU directive obligesfirms to disclose the identities of individual auditor(s)responsible for theengagement.Specifically,Article28of the directive2006⁄43⁄EC states:‘‘Where an auditfirm carries out the statutory audit,the audit report shall be signed by at least the statutory auditor(s)carrying out the statutory audit on behalf of the auditfirm.’’3.The comment period on the concept release ended on September11,2009,and according to the PCAOB’sOffice of the Chief Auditor’s standard-setting agenda,‘‘the Board’s consideration of next steps is pending further action’’(PCAOB,October2010,p.7).Available at:/News/Events/Documents/ 10132010_SAGMeeting/OCA_standards-setting_agenda.pdf.Contemporary Accounting Research Vol.29No.1(Spring2012)pp.312–340ÓCAAAdoi:10.1111/j.1911-3846.2011.01098.xAudit Partner Specialization and Audit Fees313 users,which could lead him or her to exercise greater care in performing the audit. Second,it would increase transparency about who is responsible for performing the audit, which could provide useful information to investors and,in turn,provide an additional incentive tofirms to improve the quality of all of their engagement partners.’’Some have compared the initiative to thefinancial statement certification requirement by top manage-ment stipulated in Section302of the Sarbanes-Oxley Act,arguing that it should help focus engagement partners on their existing responsibilities(see,e.g.,Carcello,Bedard, and Hermanson2009:79).4Changes in legislation and initiatives requiring the disclosure of the identities of individ-ual auditors carrying out audits implicitly acknowledge that a public company audit involves a substantial amount of work by highly skilled individual practitioners exercising their own professional judgment.It is the lead engagement partners working in the city level audit offices who play a central role in planning and implementing the audit and ulti-mately in determining the appropriate type of audit report to be issued to the client(e.g., Ferguson,Francis,and Stokes2003).Consequently,the engagement partner may play an essential role in the(perceived)audit quality beyond auditfirm size and(industry)special-ization at the national and office level and should hence not be ignored.The level of audit effort and fees depends on the client’s agency-driven demand for external auditing and on supply-side factors,such as auditfirm size,auditor expertise and auditor-perceived risk factors(e.g.,DeFond1992;O’Keefe,Simunic,and Stein1994; Gul and Tsui1998;Bell,Landsman,and Shackelford2001;Johnstone and Bedard2001, 2003;Gul and Goodwin2010;Causholli,De Martinis,Hay,and Knechel2011).From the supply-side perspective,auditors are expected to respond to the higher probability of any irregularities or accounting misstatements by increasing audit effort and charging higher fees.For instance,Gul and Tsui(1998)adopted a supply-side perspective and found that higher inherent risks associated with free cashflows are associated with higher audit effort and higher consequent fees.From the demand-side perspective,the appointment of a higher-quality auditor can serve as a signal of an enhanced quality of financial disclosure,which will potentially lead to greater value for the audit client by reducing some agency costs.Firm insiders,especially those in the heart of monitoring function(e.g.,independent directors on the boards and audit committees),may be willing to increase audit coverage to create a positive perception about thefinancial reporting quality.The positive perception will possibly facilitate thefirm to attract investments and fund profitable projects and allowfirm insiders to protect their reputation capital,avoid legal liability,and promote shareholder interests.Consistent with the demand-side per-spective,several studies report evidence suggesting that outside directors who act dili-gently demand high quality audits and pay higher audit fees(e.g.,Carcello,Hermansson, Neal,and Riley2002;Abbott,Parker,Peters,and Raghunandan2003;Knechel and Willekens2006).Auditing is generally viewed as a differentiated service with substantial variation observed in audit(effort)fees,even after controlling for observable factors such asfirm size and complexity.This differentiation allows clients some choice over the level of audit scrutiny even within audits conducted by the same(tier)auditfirms.An important means 4.Recent empirical evidence supports the view that the Sarbanes-Oxley Act Section302chief executive offi-cer(CEO)and chieffinancial officer(CFO)certification requirement had a positive effect onfinancial reporting quality.For instance,Cohen,Krishnamoorthy,and Wright(2010)report that68percent of practicing auditors interviewed believe that the certification requirement has had a positive effect on the integrity offinancial reports.Moreover,to the extent that the disclosure of engagement partner identity will increase accountability,it may thereby improve audit decisions and judgments.In particular,some studies in the auditing context report evidence indicating that accountability reduces information process-ing biases,and increases consensus and self-insight(e.g.,Johnson and Kaplan1991;Kennedy1993).CAR Vol.29No.1(Spring2012)314Contemporary Accounting Researchof audit product differentiation is through investments in specialization(Simunic and Stein1987;Liu and Simunic2005).By specializing in certain industries,certain size groups,or companies with similar risk profiles,individual auditors may be able to differ-entiate their product from those of nonspecialist audit partners(Simunic and Stein1987; Liu and Simunic2005).The Swedish Code for Corporate Governance,for instance, implicitly recognizes auditor specialization in large public companies as one relevant piece of information when assessing the quality of external auditing.5Specifically,the Code rec-ommends that information on‘‘the audit services performed by the auditor or the auditor in charge in other large companies...and other information that may be important to shareholders in assessing the competence and independence of the auditor,or auditor in charge must be disclosed in a corporate governance report on company’s homepage’’(Ori-ginal Code Sections2.3.2and2.3.3).To justify their presence in the audit market and the potential fee premiums attached to their services,the client must perceive some benefit in hiring a specialist auditor.The premium may,for instance,be attributed to the signal value of hiring a specialist auditor or to the superior advisory or other services provided by that auditor(Titman and Trueman1986).Given that a demand exists for special-ist auditors,that demand gives those auditors a greater‘‘power’’in pricing relative to nonspecialists.This paper is motivated by the lack of archival research examining issues related to engagement partner specialization.In the present study,the use of Swedish data makes it possible to construct individual audit partner client portfolios because each audit report discloses the name of the audit engagement partner.Thus,information on the identity of the audit partner in charge is observable to users offinancial statements and thereby potentially affects market-assessed perception of ex ante audit rma-tion on the sizes and compositions of the Big4audit partner-specific client portfolios provides an interesting opportunity to contribute to a more thorough understanding of auditor specialization.More specifically,it is possible to examine whether the perceived audit quality is affected not only by the brand name of thefirm,but also by the charac-teristics and reputation of the engagement partner.In essence,if auditing expertise were wholly transferable and therefore uniformly distributed across audit partners within the firm,any clientfirm would be indifferent to having any audit partner within the Big4 auditors(within a particular Big4auditfirm⁄office)to conduct the audit.Additionally, there would be no a priori reason why clients would be willing to pay any audit partner related premiums.The empiricalfindings indicate systematic differences between audit partner clienteles, suggesting audit partner specialization in different industries and in different size groups. Thisfinding is consistent with Liu and Simunic2005,who argue that auditor specializa-tion could be a competitive response by either an auditfirm or an individual audit part-ner to induce efficient audits for different types of clients,thereby gaining a limited monopoly power(and earning rents)over the clients in which they specialize.Further-more,consistent with the view that there are returns on investing in specialization,analy-ses of audit fees indicate that both audit partner industry specialization and specialization in large public companies are recognized and valued byfinancial statement users and⁄or by corporate insiders,resulting in higher fees within these engagements.According to the empirical analyses,the highest fees are earned by engagement partners who are both 5.The Swedish Corporate Governance Board is responsible for promoting and developing the Code.On July1,2005,the Stockholm Stock Exchange began applying the Swedish Code of Corporate Governance.The Code applies to all Swedish companies listed at the Stockholm Stock Exchange and foreign companies that are listed at the same exchange and whose market capitalization exceeds SEK3billion.For more information,see http://www.corporategovernanceboard.se/.CAR Vol.29No.1(Spring2012)Audit Partner Specialization and Audit Fees315 industry and publicfirm specialists.The results may be interpreted to mean that the appointment of a specialist engagement partner is associated with higher(perceived)audit quality,thus justifying the fee premium.6Collectively,thefindings of this study support the view that clientfirms infer audit quality at least to some extent from the characteris-tics of the individual audit partner in charge.The remainder of the paper is organized as follows.Section2reviews the relevant lit-erature and describes some relevant features of the Swedish audit market.Section3pre-sents the hypothesis,and section4describes the data.Section5describes the methodology used,section6presents the empirical results,and section7concludes the study.2.Literature reviewNational versus local view of the auditor–client relationshipPrior audit research literature is dominated byfirm-wide analyses treating the whole accountingfirm as the focal point and investigating whether and how auditfirm char-acteristics,such as size and industry specialization at the nationalfirm level,affect the auditor–client relationship(e.g.,Simunic and Stein1987;Francis and Wilson1988;Bec-ker,DeFond,Jiambalvo,and Subramanyam1998;Francis and Krishnan1999).All these studies implicitly assume that through standardizedfirm-wide policies and knowl-edge sharing(e.g.,through training materials,industry-specific databases,internal benchmarks for best practices,audit system programs,and internal consultative prac-tices),all audits across practice offices and audit partners within an auditfirm are uniform.7However,in practice,it is the individual audit partners from city-level practice offices who are creating and taking care of the relationship,contracting with the client,adminis-tering the audit engagement,directing the audit effort,interpreting the audit evidence,and finally issuing the appropriate audit report(Ferguson et al.2003).Because of this decen-tralized organizational structure and because individual audit partners and their character-istics vary across engagements,a research approach allowing each individual partner to be a unique and relevant unit of analysis might be a more reasonable approach than assum-ing that all audits within an auditfirm are uniform.Consistent with this intuition,a growing number of recent audit studies have changed the direction from afirm-wide to an office-level view of auditfirms(e.g.,Reynolds and Francis2000;Ferguson et al.2003;Francis,Reichelt,and Wang2005;Francis and Yu 2009;Reichelt and Wang2010;Choi,Kim,Kim,and Zang,2010).The local stream of audit literature acknowledges the likelihood that part of an auditor’s expertise is uniquely held by individual professionals through their personal knowledge of clients and cannot be 6.From the risk-based audit supply view,an alternative explanation for the observed specialist audit partnerfee premium is that the clients of specialist audit partners are systematically riskier than the clients of non-specialists in dimensions other than those already controlled for in the empirical fee model(or in thefirst-stage selection model of the Heckman two-stage approach).Despite using a two-stage Heckman1978pro-cedure and including several audit risk-related control variables in the audit fee model,the empiricalfind-ings remain susceptible to the concern that some of the omitted risk factors recognized and priced by the specialist audit partners that simultaneously determine the alignment of audit partners with engagements would explain the outcome.7.Examples of the information technology systems used in knowledge sharing include KPMG’s KWorld TM,PriceWaterhouseCoopers’s TeamAsset TM and KnowledgeCurve TM,and Ernst&Young’s Knowledge-Web TM.See Vera-Munoz,Ho,and Chow2006for factors affecting knowledge sharing within interna-tional accountingfirms,and Banker,Chang,and Kao2002for a detailed description of an international accountingfirm’s implementation of audit software and groupware for knowledge sharing.CAR Vol.29No.1(Spring2012)316Contemporary Accounting Researchreadily captured and distributed by thefirm to other offices and clients(e.g.,Ferguson et al.2003).8The results of the empirical studies adopting a local perspective tend to provide a bet-ter understanding of the operations of a Big4auditfirm than do studies taking a national perspective.For instance,there is evidence that auditors’reputation for industry expertise is neither strictly national nor strictly local in character.Auditors who are both city and industry leaders are reported to earn fee premiums both in Australia and in the United States,suggesting that there is both a national and local office reputation effect in the pric-ing of industry expertise(Ferguson et al.2003;Francis et al.2005).Moreover,both these studiesfind thatfirm-level industry specialists alone do not earn statistically significant premiums.In another study,Reichelt and Wang(2010)use U.S.data and three proxies for audit quality(abnormal accruals,clientfirms’likelihood of meeting or beating ana-lysts’earnings forecasts by one penny per share,and the propensity to issue a going con-cern audit opinion)andfind evidence consistent with the view that audit quality is higher when the auditor is both a national and city-specific industry expert.Recent and concurrent studies have pushed the local analysis still one step further to the engagement partner level.A growing number of studies use engagement partner data (mainly from Australia and Taiwan)and examine issues such as the relationship between engagement partner tenure and audit quality,producing mixedfindings(e.g.,Carey and Simnett2006;Chen,Lin,and Lin2008;Chi,Huang,Liao,and Xie2009).In a recent study,Chin and Chi(2009)use a sample of listedfirms in Taiwan to investigate the associ-ation between auditor industry expertise and restatement likelihood at the partner level and at the auditfirm level simultaneously.Their evidence suggests that the differences in restatement likelihood due to industry expertise is mainly attributable to the partner-level experts rather than to thefirm-level experts.In summary,the recent empirical evidence suggests that auditor expertise has a strong local dimension.The central conceptual question in all the national versus local studies relates to the degree to which there is a transfer of expertise from office-based accounting professionals to other auditors and offices within thefirm(Ferguson et al.2003;Francis2004).There are several factors that may deter the transfer of expertise within organizations,including audit firms(see,e.g.,Szulanski1994,2000;Nonaka and Takeuchi1995).With respect to audit firms,Vera-Munoz et al.(2006)enumerate several reasons why it is difficult for partners to share knowledge with other partners.First,a considerable amount of knowledge in audit firms can be difficult to document or transfer.9Second,even if an auditfirm manages to 8.As noted by Francis2004,another reason for this development is that Big4market shares continue toexpand globally,leading to low power in research designs of studies comparing large and small auditors because there is such low variance in the experimental variable(i.e.,most observations are audited by large Big4auditors).For instance,according to a recent Government Accountability Office(GAO) report,in2006the largest fourfirms collected94percent of all audit fees paid by public companies.More-over,according to the same report,82percent of the Fortune1000companies saw their choice of auditors as limited to three or fewerfirms,and about60percent viewed competition in their audit market as insuf-ficient(GAO2008).9.According to Polanyi1966,knowledge comes in two types:explicit and tacit.The former is amenable tocodification,while the latter is anchored in individual personal beliefs,experiences,and values.For exam-ple,knowledge of generally accepted accounting principles(GAAP)with regard to fair value requirements is explicit knowledge,while an auditor’s insights as to how a client’s management develops fair value esti-mates and whether those estimates conform to GAAP represents tacit knowledge(Vera-Munoz et al.2006).Tacit knowledge is subconsciously understood and applied and is therefore not easily articulated (Polanyi1966).Prior studies further show that most of the knowledge in any organization,including an auditfirm,is tacit knowledge(Bonner2000;Knechel2000).Consequently,because differences in knowl-edge between individual auditors within afirm lie primarily in their respective tacit knowledge,which is not easily transferred,it is unlikely thatfirm-level practices completely smooth out the differences in the levels of individual audit partner expertise.CAR Vol.29No.1(Spring2012)Audit Partner Specialization and Audit Fees317 collect extensive databases and otherfirm-wide knowledge,individual auditors still need to use their own judgment in selecting and applying relevant pieces of information given the task at hand.Third,knowledge-sharing through information technology–based expert knowledge systems is not automatically embraced by everyone.Finally,evaluation appre-hension,performance-based compensation schemes and individual auditors’pursuit of per-sonal benefits and power may deter auditors from sharing what they know.In essence, holding on to information that other peers do not have may ceteris paribus offer competi-tive advantage against those peers,when auditors,like other rational players in the econ-omy,attempt to maximize their own(economic)interests.Collectively,factors identified above may partly explain the tendency of local audit studies to provide a better understand-ing of the auditor-client relationship thanfirm-wide analyses.Factors affecting expertiseThe Merriam-Webster dictionary defines an‘‘expert’’as having,involving,or displaying a special skill or knowledge derived from training or experience.The psychological literature on expertise has reported two importantfindings relevant to the present study.First, domain-specific knowledge is the essential determinant of expertise.Second,expert knowl-edge is gained through many years of on-the-job experience(e.g.,Chi,Glaser,and Rees 1982;Glaser and Chi1988;Glaser and Bassok1989;Lapre,Mukkerjee,and Van Was-senhove2000).In other words,intensive practice and the repetition of similar tasks are required to build expertise.When applied to auditing,thesefindings suggest that having serviced many similar clients in the past may help auditors to develop a specialized knowl-edge of what these clients do and the challenges and issues they face,thereby creating in-depth knowledge of specific types of clients,leading to higher-quality audits and higher fees in these engagements.Consequently,in the present study,the terms‘‘auditor special-ization’’and‘‘auditor expertise’’are used to refer to the extent of auditors’prior audit experience with similar clients,for instance,clientfirms belonging to the same industry or size group.In other words,it is assumed that specialization is needed to gain deep exper-tise.By specializing in certain industries,certain size groups,or companies with similar risk profiles,individual auditors may be able to develop and supply the differentiated ser-vice that clients demand and that competitorsfind difficult to duplicate(Simunic and Stein 1987;Liu and Simunic2005).Moreover,auditors will only develop a specialist reputation if this increases the credibility offinancial reporting and attracts clients.Auditor specialization and audit qualityFor a long time,standard-setters,quasi-regulatory bodies,and empirical audit research have suggested that differences in the level of auditor industry expertise may be one source of variation in audit quality(Hogan and Jeter1999;Gramling and Stone2001;GAO 2008).This body of literature assumes that audit issues are nested within an industry and that accountingfirms or individual auditors with many clients within a particular industry have more opportunities to acquire the kind of profound industry knowledge that leads to industry expertise.It is also argued that the heavy investments of industry specialist audi-tors in technologies,physical facilities,personnel,and organizational control systems pro-vide them with both incentives and abilities that make them more likely than nonspecialist auditors to detect and report any irregularities or misrepresentations in clientfirms’accounts(Simunic and Stein1987).Prior archival studies tend to document a positive association between auditors’indus-try expertise and the quality offinancial reporting(e.g.,Carcello and Nagy2002,2004; Balsam,Krishnan,and Yang2003;Krishnan2003,2005;Gul,Fung,and Jaggi2009).Spe-cifically,industry specialist auditors have been found to be less likely to be associated with Securities and Exchange Commission enforcement actions(Carcello and Nagy,2004).CAR Vol.29No.1(Spring2012)318Contemporary Accounting ResearchTheir clients are also reported to have a lower probability offinancial fraud(Carcello and Nagy2004,2004),smaller amounts of abnormal accruals,and higher earnings response coefficients(Balsam et al.2003;Krishnan2003,2005).In addition,a recent study by Gul et al.2009reports evidence suggesting that auditor industry specialization is likely to reduce the association between shorter auditor tenure and lower earnings quality.Behavioral research using experimental approaches has examined industry specializa-tion at the individual auditor level.The results of these studies suggest that an individual auditor’s expertise is tied not only to each individual professional and his or her deep per-sonal knowledge of clients but also to the innate abilities of each individual(e.g.,Bonner and Lewis1990;Libby and Tan1994;Owhoso,Messier,and Lynch2002).Overall,the results of studies on auditor specialization suggest that industry specialist auditors deliver higher-quality audits than do nonspecialists and that this difference in quality is also rec-ognized by the audit market.Even though the auditor specialization literature has focused almost entirely on indus-try specialization,it is plausible that there are also other types of auditor specialization besides industry specialization.Accordingly,an investigation of the(Swedish)homepages of the Big4firms reveals that each of thefirms has structured their national practices along both industry lines and client size.All have at least two business lines based on client size:small and medium-sized companies and large public⁄international companies. All fourfirms also market a wider variety of specialized expertise,such as specialization in owner-manager companies,family businesses,public sector organizations,and nonprofit organizations.Moreover,as noted already,the Swedish Code for Corporate Governance implicitly recognizes auditor specialization in working with different size groups by recom-mending the disclosure of‘‘the audit services performed by the auditor or the auditor in charge in other large companies’’,viewing this as a relevant piece of information for users offinancial statements.Performing audits of large,complex high-profile clients is likely to require auditor expertise widely different from that required for audits of smaller and simpler closely held clients.A public listing is an important part of auditor business risk(Johnstone and Bedard2003).Because companies listed on a stock exchange receive more media attention and therefore pose a higher litigation and reputational risk,they may require a specialist auditor(Johnstone and Bedard2003).Another clear distinction between audits of public and private companies relate tofinancial reporting standards.10In Swe-den,as in all EU member countries,publicly listed companies are required to follow IFRS standards in theirfinancial reporting.Whereas Swedish private companies are also allowed to follow IFRS standards in their consolidatedfinancial statements,they tend to follow national standards(Bokfo ringsna mndens Anvisningar),which include several significant simplifications compared to IFRS.Accordingly,in the present study,com-pany size and listing status in particular is used as a proxy for client complexity and risk profile.The aforementioned differences between audits of public and private companies make it more likely that client companies will value auditor specialization in particular size groups(i.e.,public versus privatefirms).They may also suggest that specialization in a certain size group will overlap somewhat with industry specialization.It appears intuitively more valuable for publicly listed client companies seeking a higher level of audit assurance to hire an engagement partner with relevant industry experience on other large companies with similarfinancial reporting requirements,rather than hire an engagement partner with industry experience only on smaller private companies.This potential overlap is further addressed in the empirical results section below.10.I wish to thank an anonymous reviewer for making this point.CAR Vol.29No.1(Spring2012)。
多重自相关matlab
多重自相关matlab摘要：1.介绍多重自相关2.解释自相关系数3.介绍MATLAB 中的多重自相关函数4.演示如何在MATLAB 中计算多重自相关5.总结正文：1.介绍多重自相关多重自相关是指一个时间序列与其自身在未来的多个时间点的相关性。
在金融、气象和生态学等领域，研究时间序列的多重自相关性是十分重要的。
多重自相关可以帮助我们更好地理解时间序列的结构和特性，从而为预测和决策提供有力支持。
2.解释自相关系数自相关系数（Autocorrelation Coefficient）是用来衡量时间序列与其自身在未来某个时间点的相关性的一个指标。
自相关系数的取值范围为-1 到1，当自相关系数为1 时，表示序列完全正自相关；当自相关系数为-1 时，表示序列完全负自相关；当自相关系数为0 时，表示序列与自身在未来的时间点不存在相关性。
3.介绍MATLAB 中的多重自相关函数在MATLAB 中，有多重自相关函数可以用来计算时间序列的多重自相关性。
常用的函数有`acf`和`pacf`。
其中，`acf`函数用于计算自相关系数，`pacf`函数用于计算偏自相关系数。
这两个函数都需要输入一个时间序列数据，并可以返回相应的自相关系数或偏自相关系数。
4.演示如何在MATLAB 中计算多重自相关以下是一个简单的MATLAB 示例，演示如何计算时间序列的多重自相关性。
```matlab% 生成一个时间序列= 10;t = (0:n-1)"/n;x = randn(n, 1);% 计算自相关系数r = acf(x, n);% 计算偏自相关系数p = pacf(x, n);```在这个示例中，我们首先生成了一个长度为10 的时间序列，然后使用`acf`函数计算其自相关系数，使用`pacf`函数计算其偏自相关系数。
5.总结多重自相关是时间序列分析中的一个重要概念，它可以帮助我们更好地理解时间序列的结构和特性。
在MATLAB 中，我们可以使用`acf`和`pacf`函数来计算时间序列的多重自相关性。