Matlab %贰

第二章 APPLICATIONS OF MATLAB IN ENGINEERING

MATLAB Script

%：注解

%%：分节符

Relational Operators

< <= > >= == ~=(not equal to) &&(and) ||(or)

Script Flow

if elseif else

 if condition1
     statement1
 elseif condition2
     statement2
 else
     statement3
 end    %每一个区块都需要一个end
 %ram(a,2)取余，a/2的余数
 %disp('')输出语句，disp()输出变量

switch

 switch expression
 case value1
     statement1
 case value2
     statement2
     …………
 otherwise
     statement
 end

while

 while expression
     statement
 end
 EG:
 n = 1;
 while prod(1:n) < 1e100     %prod累积
     n = n+1;
 end

for

 for variable=start:increment:end
     commands
 end
 EG:
 for n=1:10    %1:2:10
     a(n) = 2^n;
 end
 disp(a)     %disp(find(a))

Pre - allocationg(节约时间)

 Not pre-allocating
 tic
 for ii = 1:2000
     for jj = 1:2000
         A(ii,jj) = ii+jj;
     end
 end
 toc
 Pre-allocating
 tic
 A = zeros(2000, 2000);
 for ii = 1:size(A,1)
     for jj = 1:size(A:2)
         A(ii,jj) = ii+jj;
     end
 end
 toc
 %tic---toc为计时组件

break ==> while

 x = 2; k = 0; error = inf;
 error_threshold = 1e-32;
 while error_threshold
     if k>100
         break
     end
     x = x-sin(x)/cos(x);
     error = abs(x-pi);
     k = k+1;
 end

注：clear all：清楚变量

close all：关闭图形

Ctrl + C：避免宕机，跳出程序

Function

 edit(which('mean.m'))   %进入一个mean function的源码
 function y = mean()
 %……
 %……
 %……
 if nargin == 1 || (nargin == 2 && isDimSet)
 ……………………

Default Variables

nargin：Number of function input arguments

 function [volume] = pillar(Do, di ,height)
 if nargin == 2
     haight = 1;

nargout：Number of function output arguments

varargin、varargout：Variable length input/output argument list

inputname：Variable name of function input

mfilename：File name of currently running function

Handles

 f = @(x) exp(-2*x);   %f指向后面的exp(……)，@(x)是f的input
 x = 0:0.1:2;
 plot(x,f(x));   %画图
 %将X于f(x)绑定，将x放入对应法则中