vectors must be the same lengths error with subplot

Question

Anna 2014-9-11

评论： Anna 2014-9-11

I am new to MatLab and am unsure what is causing the error in my code. I get the vectors must be the same lengths error message. The code is below.

y1=0.5.*x.^2 x1=-5:0.25:5 y2=-x x2=0:2:100 figure subplot(2,1,1); plot(x1,y1) subplot(2,1,2); plot(x2,y2)

Answer 1

Julia 2014-9-11

Hi,

What size has the vector x? y1 and y2 have the same size as x. But the sizes of x1 and x2 are not the same:

length(x1) = 41
length(x2) = 51

But since y1 and y2 have the same size, x1 and x2 need to have the same size as them.

This could work if

length(x)=41 :
x1=-5:0.25:5
x2=0:2:80
length(x1) = 41
length(x2) = 41

Anna 2014-9-11

The assignment required x2 go up to 100 but using x2=0:2.5:100 and keeping x1 the same accomplishes this as well. Thanks for the explanation!

Answer 2

Mischa Kim 2014-9-11

Anna, you need to define x1 and x2 first before you can use the variables to compute y1 and y2. Use something like

 x1 = -5:0.25:5;
 y1 = 0.5.*x1.^2;
 x2 = 0:2:100;
 y2 = -x2;
 figure
 subplot(2,1,1); 
 plot(x1,y1) 
 subplot(2,1,2); 
 plot(x2,y2)