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matlab基础

分类: 文章 • 2025-02-04 09:58:16

matlab代码发布成网页形式

matlab基础

%%之间要打一个空格，表示每一个模块的名称。 

以下是发布的内容：

Contents

I. 清空环境变量及命令

clear all

clc

II. MATLAB编程习惯与风格 

x_coordinate = rand(1,10);
y_coordinate = rand(1,10);
figure
plot(x_coordinate,y_coordinate,'r-*')

matlab基础

III. MATLAB程序调试

%% % 1. Index must be a positive integer or logical. A = [1 2 3 4 5]; A(0) A(3.5) A(-2)

%% % 2. Undefined function or variable 'B'. B

%% % 3. Inner matrix dimensions must agree. B = [1 2 3]; A * B

%% % 4. Function definitions are not permitted at the prompt or in scripts. function c = add(a,b) c = a + b;

%% % 5. Index out of bounds because numel(A)=5. A(6)

%% % 6. In an assignment A(I) = B, the number of elements in B and I must be the same. A(3) = B;

%% % 7. Expression or statement is incorrect--possibly unbalanced (, {, or [. mean(A(1:3)

%% % 8. Too many input arguments. mean(A,1,2)

9. 循环体的调试

a = 1:100;
b = [];
for i = 21:21
    index = 105 - 5*i;
    b = [b a(index)];
end

Subscript indices must either be real positive integers or logicals.

Error in Example_2 (line 55)
    b = [b a(index)];

10. 查看、编辑MATLAB自带的工具箱函数

edit mean

edit newff

III. MATLAB内存优化配置 

feature memstats
%

IV. 向量化编程

1. 及时清除不用的变量

a = rand(10000);
b = rand(10000);
clear a
b = rand(10000);

2. 使用变量前，预分配内存空间

clear all
clc
n = 30000;
tic;
for k = 1:n
    a(k) = 1;
end
time = toc;
disp(['未预分配内存下动态赋值长为',num2str(n),'的数组时间是:',num2str(time),'秒！'])

tic
b = zeros(1,n);
for k = 1:n
    b(k) = 1;
end
time = toc;
disp(['预分配内存下动态赋值长为',num2str(n),'的数组时间是:',num2str(time),'秒！'])

%%c
% 3. 选择恰当的数据类型
clear all
clc
n = 300000;
a = 8;
b{1} = 8;
c.data = 8;

tic
for k = 1:n;
    a;
end
time = toc;
disp(['访问',num2str(n),'次double型数组时间是:',num2str(time),'秒！'])

tic
for k = 1:n;
    b{1};
end
time = toc;
disp(['访问',num2str(n),'次cell型数组时间是:',num2str(time),'秒！'])

tic
for k = 1:n;
    c.data;
end
time = toc;
disp(['访问',num2str(n),'次struct型数组时间是:',num2str(time),'秒！'])

4. 按列优先循环

clear all
clc
n = 1000;
a = rand(n);
tic
for i = 1:n
    for j = 1:n
        a(i,j);
    end
end
toc

for i = 1:n
    for j = 1:n
        a(j,i);
    end
end
toc

5. 循环次数多的变量安排在内层

clear all
clc
tic
a = 0;
for i = 1:1000
    for j = 50000
        a = a + 1;
    end
end
toc

tic
a = 0;
for i = 1:50000
    for j = 1:1000
        a = a + 1;
    end
end
toc

6. 给一些函数“瘦身”

edit mean
clear all
clc
a = rand(1,10000);
tic
b = mean(a)
toc

tic
c = sum(a)/length(a)
toc

V. 图像对象和句柄

1. 如何设置线条的属性呢？

x = 0:0.01:2*pi;
y = sin(x);
h = plot(x,y);
grid on
get(h)
set(h,'linestyle','-','linewidth',2,'color','k')

2. 如何修改网格的间隔呢？

set(gca,'xtick',0:0.5:7)
set(gca,'ytick',-1:0.1:1)

3. 如何设置图例的字体及大小呢？

x = 0:0.01:2*pi;
y1 = sin(x);
y2 = cos(x);
plot(x,y1,'r')
hold on
plot(x,y2,'-.b')
h = legend('sin(x)','cos(x)');
set(h,'fontsize',16,'color','k','edgecolor','r','textcolor','w')

4. 如何拆分图例呢？

x = 0:0.01:2*pi;
y1 = sin(x);
y2 = cos(x);
h1 = plot(x,y1,'r');
hold on
h2 = plot(x,y2,'-.b');
ax1 = axes('position',get(gca,'position'),'visible','off');
legend(ax1,h1,'sin(x)','location','northwest')
ax2 = axes('position',get(gca,'position'),'visible','off');
legend(ax2,h2,'cos(x)','location','northeast')

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