# Issue with numerical integration of two variable function

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Bathala Teja on 20 Sep 2021
Commented: Bathala Teja on 22 Sep 2021
I want to do integration of two variable function w.r.t one variable.
A = @(x, y)cos(x)+sin(y)
A = function_handle with value:
@(x,y)cos(x)+sin(y)
B = @(x, y)(A-integral(@(x)A, 0 , 2*pi))
B = function_handle with value:
@(x,y)(A-integral(@(x)A,0,2*pi))
How to see the output here??

Walter Roberson on 20 Sep 2021
A = @(x, y) cos(x)+sin(y)
A = function_handle with value:
@(x,y)cos(x)+sin(y)
B = @(x, y) A(x,y)-integral(@(X)A(X,y), 0 , 2*pi, 'ArrayValued', true)
B = function_handle with value:
@(x,y)A(x,y)-integral(@(X)A(X,y),0,2*pi,'ArrayValued',true)
Warning: Reached the limit on the maximum number of intervals in use. Approximate bound on error is 1.1e-07. The integral may not exist, or it may be difficult to approximate numerically to the requested accuracy.
Warning: Reached the limit on the maximum number of intervals in use. Approximate bound on error is 1.1e-07. The integral may not exist, or it may be difficult to approximate numerically to the requested accuracy.
fsurf(B, [-pi pi -pi pi])
Bathala Teja on 22 Sep 2021
ok got it
thank you

Sargondjani on 20 Sep 2021
Edited: Sargondjani on 20 Sep 2021
You created only function handles. So f(x,y) = .....
To compute the numerical value you need to assign numerical values to x and y. So for example:
y=0;
x=1;
B_value = B(x,y);

Steven Lord on 20 Sep 2021
A = @(x, y)cos(x)+sin(y);
B = @(x, y)(A-integral(@(x)A, 0 , 2*pi));
Your expression for B won't work for two reasons. The integral function requires the function handle you pass into it as the first input to return a numeric array, but yours returns a function handle. Even if that worked, you would then try to subtract that result from a function handle and arithmetic on function handles is not supported.
From your description it sounds like you want B to be a function of one variable, but you need to pass two inputs into your A function handle. Assuming you want to fix the value of x and make B just a function of y, evaluate A inside your expression for B:
A = @(x, y)cos(x)+sin(y);
fixedX = 0.5;
B = @(y) A(fixedX, y)-integral(@(z)A(fixedX, z), 0 , 2*pi)
B = function_handle with value:
@(y)A(fixedX,y)-integral(@(z)A(fixedX,z),0,2*pi)
B(0.25)
ans = -4.3890
Bathala Teja on 21 Sep 2021
My intension is to get B as a function of x and y not interms of value

R2021a

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