how to calculated integral of multiplying two function handle that changed by loop

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mohammad m
mohammad m 2016-12-12
编辑： Walter Roberson 2017-1-4
hi guys
i have two function like these:
f(x,y)=(i+1)x+(j-1)y
g(x,y)=(i-1)x+(j-1)y
(real functions are more complex that here)
now i want to calculate integral of h(x,y)=f*g when f & g change by loops depend on i & j.
i want to write these function in a new mfile & use of them in my code. but i don't know hoe i can do this.
actually i want do like bellow.
for i=1:n
for j=1:m
h=@(x,y)(f*g)
l=integral2(h,-1,1,-1,1)
end
end
that f & g are functions like this.
function d=f(i,j)
f(x,y)=(i+1)*x+(j-1)*y
end
i know cods are incorrect but wrote these to saying what i want to do.
function are complex & i should use them several times in my code so i cant write them in it.
thank u for answering :)

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回答（2 个）

Walter Roberson
Walter Roberson 2016-12-12
h = @(x, y) f(x, y).*g(x,y);
  1 个评论
mohammad m
mohammad m 2016-12-14
编辑：mohammad m 2016-12-14
hi thank you for answering. when i use this code an error like bellow occurred when i edit my code like you.
Undefined function or variable 'x'.
then for calculate integral of (f*f), i change my code like below :
for i=1:2
for j=1:2
h=@(x,y)f(i,j).*f(i,j);
l=integral2(h,-1,1,-1,1)
end
end
and function f in another mfile like below
function d=f(i,j)
d=@(x,y)(i+1)*x+(j-1)*y
end
now i get this error:
Undefined function 'times' for input arguments
of type 'function_handle'.
Error in @(x,y)f(i,j).*f(i,j)
Error in integral2Calc>integral2t/tensor (line
229)
Z = FUN(X,Y); NFE = NFE + 1;
Error in integral2Calc>integral2t (line 56)
[Qsub,esub] = tensor(thetaL,thetaR,phiB,phiT);
Error in integral2Calc (line 10)
[q,errbnd] =
integral2t(fun,xmin,xmax,ymin,ymax,optionstruct);
Error in integral2 (line 106)
Q =
integral2Calc(fun,xmin,xmax,yminfun,ymaxfun,opstruct);
Error in Untitled4 (line 6)
l=integral2(h,-1,1,-1,1)
i don't know how to make new functions by loop & how to multiply them & how to integrate new function. i'm using matlab 2013

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Steven Lord
Steven Lord 2016-12-14
A 1-dimensional example:
fun1 = @(x) sin(x);
fun2 = @(y) cos(y);
fun3 = @(z) fun1(z).*fun2(z);
integral(fun3, 0, 1)
To check, explicitly specify the function in the integral call:
integral(@(x) sin(x).*cos(x), 0, 1)
Another check is to perform the integration symbolically with the int function from Symbolic Math Toolbox. The vpa call just displays the answer in a format that's easier to compare with the numeric answers.
syms q
vpa(int(sin(q)*cos(q), q, 0, 1))
  1 个评论
mohammad m
mohammad m 2016-12-14
thank you for answering. my function change by loop & are complex, i'm trying to don't use of syms, because syms reduce speed, so i'm trying to find a way by function handle or any other way that can calculate multiplying & integration of parametric functions that change by loop.

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