Thread: URGENT: MATLAB quad function frustration

Hi all,

I'm trying to use the built-in MATLAB function quad to integrate the following function :


but its not working for me.

Now when I use the quad function to evaluate

I get the correct answer.

When I use the quad function to evaluate

I get the correct answer.

but when I use the quad function to evaluate



I get the output

??? Error using ==> mtimes
Inner matrix dimensions must agree.

Error in ==> myfun at 7
y = sin(x) * x ;

Error in ==> quad at 77
y = f(x, varargin{:});

where myfun is the mfile I wrote .........

function y = myfun(x)
y = sin(x) * x ;


Also this is what I type into the MATLAB command window when I try and use the quad function

Q = quad(@myfun,0,(2*pi))


What am I doing wrong here? Im no expert in MATLAB and Im not sure how to get around this.

Nevermind, I realised that I had to vectorize my mfile by changing it to

function y = myfun(x)
y = x.*sin(x);

Originally Posted by woody198403

Hi all,

I'm trying to use the built-in MATLAB function quad to integrate the following function :


but its not working for me.

Now when I use the quad function to evaluate

I get the correct answer.

When I use the quad function to evaluate

I get the correct answer.

but when I use the quad function to evaluate



I get the output

??? Error using ==> mtimes
Inner matrix dimensions must agree.

Error in ==> myfun at 7
y = sin(x) * x ;

Error in ==> quad at 77
y = f(x, varargin{:});

where myfun is the mfile I wrote .........

function y = myfun(x)
y = sin(x) * x ;


Also this is what I type into the MATLAB command window when I try and use the quad function

Q = quad(@myfun,0,(2*pi))


What am I doing wrong here? Im no expert in MATLAB and Im not sure how to get around this.

u need to put dot before multiplication sign(array)...try this

Originally Posted by woody198403

Hi all,

I'm trying to use the built-in MATLAB function quad to integrate the following function :


but its not working for me.

Now when I use the quad function to evaluate

I get the correct answer.

When I use the quad function to evaluate

I get the correct answer.

but when I use the quad function to evaluate



I get the output

??? Error using ==> mtimes
Inner matrix dimensions must agree.

Error in ==> myfun at 7
y = sin(x) * x ;

Error in ==> quad at 77
y = f(x, varargin{:});

where myfun is the mfile I wrote .........

function y = myfun(x)
y = sin(x) * x ;


Also this is what I type into the MATLAB command window when I try and use the quad function

Q = quad(@myfun,0,(2*pi))


What am I doing wrong here? Im no expert in MATLAB and Im not sure how to get around this.

function y = myfun(x)
y = sin(x) .* x ;

CB