Partial integration
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I have integrate twice, but IT IS NOT a double integral (which would be easy with quad2d or dblquad), but its smth like this: int(a->b)(f(x) * int(c->d)(g(x,x') dx')dx)
so basicly, i need to partialy integrate g(x,x') by x':c->d, then multiply with f(x), and integrate with x:a->b)
and after a few hours spent on this website and searching the matlab documentation and finding nothing of use, i decided to ask here. thanks for any help!
1 Comment
Bjorn Gustavsson
on 13 Jul 2011
Come to think of it it actually is a double integral:
\int_a^b f(x)*\int_c^d g(x,x')dx' dx = \int_a^b \int_c^d f(x)*g(x,x')dx' dx
Accepted Answer
Tomislav Broni?
on 12 Jul 2011
1 Comment
Bjorn Gustavsson
on 13 Jul 2011
Nowhere in your example did I see any matrices of functions, so obviously I could not guess stat you had such a problem, only that you wanted to integrate someting like this:
\int_a^b f(x)*\int_c^d g(x,x')dx' dx
So this is what I gave you.
More Answers (3)
Bjorn Gustavsson
on 11 Jul 2011
Maybe something based on this pattern would work:
g = @(x,xp) (x-xp).^2;
f = @(x) x;
IntOfG = @(x,c,d) quadgk(@(xp) g(x,xp),c,d);
res = quadgk(@(x) f(x).*IntOfG(x,c,d),a,b);
0 Comments
Tomislav Broni?
on 11 Jul 2011
1 Comment
Bjorn Gustavsson
on 12 Jul 2011
Hi,
If you read the help for quadgk you see that the first argument should be a function.
Since you don't show me how f1 is defined I can't know why you get that error. If you try to test/evaluate the functions you define step by step (in my example g, f and IntOfG) you can at least make sure that they work. The only thing I can say is that my example works in matlab R2009a.
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