# integration of FFT

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Anita on 19 Dec 2014
Commented: Anita on 19 Dec 2014
I am supposed to calculate the fft of a rect function, and then getting the integration of answer. what I have done is :
fs = ceil(4*pi)+1;
xend = 3;
t = (0:1/fs:xend-1/fs)-1/3*xend;
x_f = zeros([1,fs*xend]);
x_f(1,(1/3*xend*fs):(2/3*xend*fs-1)) = 5.7737e19.*ones([1,(1/3*xend*fs)]);
m_f = length(x_f);
n = pow2(nextpow2(m_f))*4;
y = fft(x_f,n);
f = (0:n-1)*(fs/n);
power = y.* conj(y)/n;
y0 = fftshift(y); f0 = (-n/2:n/2-1)*(fs/n)/pi;
power0 = abs(y0);
plot(f0,power0);
K_fourier=power0;
K_int = int(K_fourier, -pi, pi);
then, I have this error: Undefined function 'int' for input arguments of type 'double'.
Thank you

Star Strider on 19 Dec 2014
Use the trapz function.

Thorsten on 19 Dec 2014
The is no such function as int in Matlab. What is int supposed to do?
Anita on 19 Dec 2014
numerical integration.

Shoaibur Rahman on 19 Dec 2014
Edited: Shoaibur Rahman on 19 Dec 2014
K_fourier is double type in your code. int cannot take double type as the function.
@ Thorsten: int performs all symbolic, definite, and indefinite integration of a function defined, and given as the input argument to int.
Anita on 19 Dec 2014
Thanks for your answer. Well, I'm aware about it and searching for a way to get the integration somehow. do you have any idea if it is possible to get integral of a 1x256 complex double or any other way to solve this problem?