# problems of this function

14 views (last 30 days)
Reopened: HADIMARGO on 18 Dec 2018
i want to draw this function but my code has an error:
code:
x=linspace(-5,5,1000);
n=double(1:1:100);
l=2;
f=sin(x);
g=cos(x);
s=0;
landa=((n*pi)/l );
a=(2/l)*int(f.*sin((n*pi)/l)*x,0,l);
b=(2/(l*landa))*int(g*sin((n*pi*x)/l,0,l));
for n=1:1:1000
p=((a*cos(landa*t)+ b*sin(landa*t))*sin((n*pi*x)/l));
s=s + p;
end
plot (x,t,s)
error:
>> f1
Matrix dimensions must agree.
Error in f1 (line 8)
a=(2/l)*int(f.*sin((n*pi)/l)*x,0,l);
where is the problem of this error and code?

Jan on 14 Dec 2018
Use the debugger to find the problem. Type this in the command window:
dbstop if error
Then run the code again until it stops at the error. Now split the command into parts and check them in the command window:
% a = (2 / l) * int(f .* sin((n * pi) / l) * x, 0, l);
size(2 / l)
size((n * pi) / l)
size(sin((n * pi) / l) * x) % I assume this fails
size(f)
size(f .* sin((n * pi) / l) * x)
This method let you identify, which part causes the error message. This should help you to fix the problem.
It looks strange that you define n as vector at first and use it a loop index again. I guess you want to calculate the integrals inside the loop.