I have a problem with integration "Error using / Matrix dimensions must agree"

syntax is here:

clc;clear all;close all;
m=input('input a value');
x=linspace(1,2,m);
%function
f=(x+(1/x)).^2;
%real value of integral
ff=@(x)(x+(1/x)).^2;
RV=integral(ff,1,2);
%Solution with numerical method (Trap method)
IT=Trap(x,f,m)
ybh=100*(abs(RV-IT)/RV

function IT=Trap(x,f,m)
IT=(x(m)-x(1))*(f(1)+f(m))/2
return
end

Why this isnt working?

ERROR:

input a value2

Error using /

Matrix dimensions must agree.

Error in odev (line 5)

f=(x+(1/x)).^2;

Thank you.

Answer 1

[Fabio Freschi]

When you define your functions use ./ instead of /

%function
f=(x+(1./x)).^2;
%real value of integral
ff=@(x)(x+(1./x)).^2;

[Filious]

I already tried that I still got same error

[Fabio Freschi]

I don't see any error with my correction. I can't check all the code because you didn't share your Trap function. If you can attach it, I can try to check it out

[Jan]

@Filious: Then please post the current version of your code an a copy of the complete error message.

[Fabio Freschi]

I did not check the correctness of the results, but the code runs without problems, e.g. no errors, when you change the functiond definitions as I said

%function
f=(x+(1./x)).^2;
%real value of integral
ff=@(x)(x+(1./x)).^2;

And you close the bracket in the last line

ybh=100*(abs(RV-IT))/RV

[Fabio Freschi]

Maybe I got the point: your code does not exit with an error, but it produces the wrong result!

Your implementation of the trapezoidal rule is not correct. You are not using all your samples but only the first and last points. If you really don't want to use the built-in trapz, you can implement yourself as

Itrap = sum((f(2:end)+f(1:end-1)).*(x(2:end)-x(1:end-1))/2)

[Filious]

Thank you. You were very helpful. It turns out I didnt try your correction exacly