# FFT of a row of data (for a beginner)

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cosined on 16 Nov 2015
Commented: cosined on 17 Nov 2015
Hello, I am an undergraduate student and I want to use the fft function to change a row of data points from the time domain to the frequency domain and then get the power spectrum. The row in question is a 1x600010 matrix of int16 type, taken from a 16x600010 int16 matrix. Right now my code is:
limits = [1 600010];
figure(1)
x = (1:600010);
y = double(Data(1,:))
plot(x,y,'r');
xlim(limits);
fs = 1000;
t = 0:1/fs:600010-1/fs;
m = length(y);
n = pow2(nextpow2(m));
Y = fft(y,n);
f = (0:n-1)*(fs/n);
power = Y.*conj(Y)/n
figure(2)
plot(f,power)
MATLAB says that there is an error in this line: Y = fft(y,n) because 'fft' is an undefined function for input arguments of type 'int16'. How do I change the type of the matrix for it to be compatible with the code, if possible?

Joseph Cheng on 16 Nov 2015
Edited: Joseph Cheng on 16 Nov 2015
convert the data using the function double()
y = double(Data(1,:))
you can read up on the different types of numbers and changing of types here: http://www.mathworks.com/help/matlab/numeric-types.html.
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cosined on 17 Nov 2015
Thank you Joseph!

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