Question

matlab 用if编简单的 分段函数

function [Y]= thli(X)
%UNTITLED Summary of this function goes here
% Detailed explanation goes here
%x = 0:0.1:1
if X<=0.1
Y=1000*X;
end
if X>0.1 && X<=0.2
Y=2*50000*(X-0.1)+100;

end
if X>0.2 && X<=0.25
Y=50*50000*(X-0.2)+2*50000*0.1+100;
end
if X>0.25
Y=100;
end
end
总是出错：??? Input argument "X" is undefined.

Error in ==> thli at 5
if X<=0.1
求高手帮忙，谢谢啦；
谢谢你的帮忙，不过结果运行怎么基本是0啊。
ans =
Columns 1 through 16
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Columns 17 through 32
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Columns 33 through 48
0 0 0 0 0

Answer 1

比如这个例子：

1、打开MATLAB软件，粘贴以下代码：

clc; clear all

x=0:0.01:10;

y=sqrt(x).*(x>=0&x<4)+2*(x>=4&x<6)+(5-x/2).*(x>=6&x<8)+1*(x>=8);

plot(x,y,'r','linewidth',2)

axis([0 10 0 2.1])

grid on

解释一下，代码的逻辑运算符是这个程序成败的关键，利用了判断逻辑数和向量之间的相乘，构造分段函数的表达式.

2、点击运行，即可以得到分段函数的图像了：

Answer 2

！！！应该是这样的结果吧！！！！

程序如下：
function y= thli(x)
%UNTITLED Summary of this function goes here
% Detailed explanation goes here
%x = 0:0.1:1
if x<=0.1
y=1000*x;
elseif x>0.1
y=2*50000*(x-0.1)+100;
elseif x<=0.2
y=2*50000*(x-0.1)+100;
elseif x>0.2
y=50*50000*(x-0.2)+2*50000*0.1+100;
elseif x<=0.25
y=50*50000*(x-0.2)+2*50000*0.1+100;
elseif x>0.25
y=100;

end

Answer 3

function [y,x]= thli(x)
%UNTITLED Summary of this function goes here
% Detailed explanation goes here
if nargin==0
x = 0:0.01:1;
end
for i=1:length(x)
X=x(i);
if X<=0.1
Y=1000*X;
end
if X>0.1 && X<=0.2
Y=2*50000*(X-0.1)+100;

end
if X>0.2 && X<=0.25
Y=50*50000*(X-0.2)+2*50000*0.1+100;
end
if X>0.25
Y=100;
end
end
y(i)=Y;
end

%%%%%%%%%%%
调用一下啊！
我是这样用的。
[y,x]= thli();plot(x,y)
你看看结果吧