help with numerical integration

I want to numerically integrate a function where a parameter is varied. This is what my code looks like:

y=0:0.0001:30.5;
r=30.5:0.0001:sqrt((y).^2+(25.4)^2);
Sa=3.1381e5;
f=(Sa/2)*(1./(r).*exp(-0.1577534.*r));
F=trapz(r,f)

What I'm trying to tell matlab is to find F for each of the y-values listed. I want matlab to list the array of which y-values were used and the corresponding F for that y-value.

As it is when I enter my code my F is 0.

Answer 1

[Amit]

First thing: what are you trying to do with y and r? Your r will be empty as the last value in defining r is a vector.

Can you write down what is the correlation in r and y?

[richard]

This is what I wanted my 'bounds of integration' to look like, which was what my r was supposed to represent:

y=0:0.0001:30.5;

0 ----> sqrt((0)^2 + (25.4)^2) this corresponds to the F when my y=0

0.0001--->sqrt((0.0001)^2 +(25.4)^2)this corresponds to the F when my y=0.0001

0.0002 --->sqrt((0.0002)^2 + (25.4)^2) this corresponds to the F when my y=0.0002

y_n--->sqrt((y_n)^2 + (25.4)^2) this corresponds to the F when my y=y_n

and so on until my y=30.5

Please let me know if you understand what I am writing out

[Amit]

y=0:0.0001:30.5;
r = sqrt((y).^2+(25.4)^2);
Sa=3.1381e5;
f=(Sa/2)*(1./(r).*exp(-0.1577534.*r));
F=trapz(r,f)