# I just want to know the reason why the integral function doesn't work this way?

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Harsha vardhan naidu on 15 Apr 2020
Commented: Steven Lord on 15 Apr 2020
%p is a function handle so what's the problem.
Now i am working on finding response of the rectangular plate. So, after solving I get a function as an output and I gotta integrate that function between a certain interval to find a constant. So let us assume f is the function i got as an output. If i give f as an input to integral function I am geting an error saying "FUNCTION PASSED TO INTEGRAL FUNCTION MUST BE A FUNCTION HANDLE" so i created another variable p and made it a function handle now i am getting an error saying "INPUT FUNCTION MUST RETURN SINGLE OR DOUBLE VALUES. FOUND SYM". Looking for someone's help. Any way to solve this issue?
syms x;
f= x^2;
p = @(x) f;
q = integral(p,0,1)

Bjorn Gustavsson on 15 Apr 2020
You have to convert the symbolic function to a function-handle that returns a scalar double. You can do this for your example problem:
F = matlabFunction(f);
q = integral(F,0,1);
The first step converts the symbolic expression into a matlab-function-handle.
HTH
Steven Lord on 15 Apr 2020
Another alternative, if you want to perform the integration symbolically, would be to call the int function instead of integral. The signature is slightly different (you need to specify the variable over which you're integrating) but they're still quite similar.
syms x
f = x^2;
int(f, x, 0, 1)

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