# Interpolating Data with the Discrete Fourier Transform

1. Jul 2, 2013

### zs96742

Hello everyone:

I have some question using the FFT in matlab for data interpolating. I don't know what the relation between the normal fourier series and the real, image number.

For example, given a set of measurement data, I can use the curve fitting toolbox to fit a curve.
The general equation is f(x) = a0 + a1*cos(x*w) + b1*sin(x*w) + a2*cos(2*x*w) + b2*sin(2*x*w) for a a factor 2 fourier series. The a0,a1,b1,a2,b2 and w can be obtained.

When I use the FFT function, it returns the Fourier transform of each column of the matrix. This matrix has real and imaginary part.

Are their any relationship between those two results ? if yes, what should I do to convert the FFT results into a normal fourier series format?

2. Jul 3, 2013

### mathman

Usually when you have a Fourier transform with real and imaginary parts, the real part is the cosine transform and the imaginary part is the sine transform.

However I am not familiar with the specific algorithm, so I could be completely wrong.