第1章-Matlab简介

流程控制
if … elseif … else …
for
while switch … case … otherwise … break
continue try … catch …
Script locations
设置search path
Help and documentation
doc mean help mean
字符串
• mytext = ‘Hello, world!’ • otherText = ‘You’’re right’ • longText = [myText, ‘ – ‘, otherText] % concatenate strings with square brackets • f = 71; c = (f - 32) / 1.8; • tempText = [‘Temperature is ‘, num2str(c), ‘C’]
Color specification
Specifier y m Color yellow magenta
c r g b
w k
cyan red green blue
white black
Hold on / hold off
• x = 0:pi/20:2*pi; • y = sin(x); • plot(x, y, ‘m-*’) • hold on • y2 = cos(x); • plot(x, y2, ‘c--o’)
数字图像处理
第 1 章 MATLAB 简介
赵毅力 ylzhao@
MATLAB是什么？
• MATLAB是一个科学计算和仿真模拟的软件平台，由 一系列工具箱组成：
• • • • • • • • • • Aerospace Toolbox Antenna Toolbox Bioinformatics Toolbox Communications System Toolbox Computer Vision System Toolbox Image Processing Toolbox Control System Toolbox Curve Fitting Toolbox Data Acquisition Toolbox …
• /
MATLAB - Matrix Laboratory
Evolution of MATLAB
变量赋值
• a=1
• b=2 • c=a+b • d = cos(a)
• sin(a)
• e = a * b;
矩阵和数组
• A = [1 2 3 4] % row vector • B = [1 2 3; 4 5 6; 7 8 9] % 2D matrix • Z = zeros(5, 1) • C = A + 10 • D = sin(A) • E = B’ % 转置
函数调用
• A = [1 3 5]; • maxA = max(A) • C = [10 6 4]; • maxC = max(A, C) • [maxA, loc] = max(A) % with location • disp(‘hello world’) % display string
• clc % clears the Command Window
Matrices and magic squares
• 矩阵是二维数组 • 1x1的矩阵称为标量 • 只有一行或者一列的矩阵称为向量
Entering matrices
• A = [16 3 2 13; 5 10 11 8; 9 6 7 12; 4 15 14 1] A= 16 3 5 10 9 6 4 15 2 13 11 8 7 12 14 1
% Draw a line from (0,m) to (n,m) m = mean(r); hold on plot([0,n],[m,m]) % x1=0,x2=n,y1=m,y2=m hold off title('Mean of Random Uniform Data')
Loops and Conditional Statements
工作区变量 - Workspace Variables • whos • save myfile.mat % save data as MAT-file • clear % clear all the variables
• load myfile.mat % Restore data from a MAT-file
The magic function
• 14 A=
16 3 5 10 9 6 4 15
3 13 10 8 6 12 15 1
2 13 11 8 7 12 14 1
Matrix reorder
• C = B(:, [1 3 2 4]) % reorder
绘制SINE函数图形
Line specification
Specifier -: -. Line Style Solid line Dashed line Dotted line Dash-dot line
Marker specification
Specifier o + * . x s Marker Circle Plus sign Asterisk Point Cross Square
C=
16 3 5 10 9 6 4 15 A=
16 3 5 10 9 6 4 15
2 13 11 8 7 12 14 1
2 13 11 8 7 12 14 1
Generating matrices
• zeros - All zeros • ones - All ones • rand - Uniformly distributed random elements • randn - Normally distributed random elements
• F = inv(B) % 逆矩阵 • P = B * E % matrix multiplication • W = B .* B % element-wise multiplication
• A.^3
连接 - Concatenation
• A = [1 2 3; 4 5 6; 7 8 10] • A1 = [A, A] % 水平方向连接 • A2 = [A; A] % 垂直方向连接
Building tables
•
n = (0:9)‘
• pows = [n n.^2 2.^n]
pows =
0 1 2 3 4 5 6 7 8 9
0 1 1 2 4 4 9 8 16 16 25 32 36 64 49 128 64 256 81 512
Functions
help elfun
help specfun
绘图
• x = 0:pi/100:2*pi; • y = sin(x) • plot(x, y) • xlabel(‘x’) • ylabel(‘sin(x)’) • title(‘Plot of the Sine function’)
绘制SINE函数图形
绘制SINE函数图形
• plot(x, y, ‘r--’)
复数
• sqrt(-1) • C = [3+4i, 4+3j; -i, 10j]
数组索引 - Array indexing
• A = magic(4) • A(4, 2) % row and column subscripts • A(8) % linear indexing
• A(4, 5) % Index exceeds matrix dimensions • A(1:3, 2) % use colon to index range • A(3, :) • C = 0:10:100 % start:step:end • D = 0:10
子图 - subplot
Programming and scripts
• edit plotrand
% Generate random data from a uniform distribution % and calculate the mean. Plot the data and the mean. n = 50; r = rand(n, 1); plot(r)
Logical subscripting
• x = [2.1 1.7 1.6 1.5 NaN 1.9 1.8 1.5 5.1 1.8 1.4 2.2 1.6 1.8]; • ind = isfinite(x); % logical array • x(ind)
• ind2 = isnan(x); % logical array • x(ind2)
sum, transpose, and diag
• sum(A) ans = 34 34 34 34
sum, transpose, and diag
• A’ ans = 16 5 3 10 2 11 13 8 9 4 6 15 7 14 12 1
sum, transpose, and diag
• sum(A')' ans = 34 34 34 34
sum, transpose, and diag
• sum(A, 2) % specify dimension argument ans = 34 34 34 34
sum, transpose, and diag
• sum(diag(A)) ans = 34
Logical operations
Functions
A & B, and(A, B)
Meaning
Logical AND
~A, not(A) A | B, or(A, B)