# Discrete Fourier Transform Frequency

1. Mar 13, 2010

### Chemistopher

Hi everybody,

I'm in the process of writing a discrete Fourier transform program using the algorithm on the DFT wikipedia page. When I throw in functions that I know the frequency domain signal of it gives the predicted shape but I have absolutely know idea how to generate a frequency axis.

Does anybody here know how I can compute the frequency values?

Chris

2. Mar 14, 2010

### Redbelly98

Staff Emeritus
Try using a sine function at a specific frequency. Then whatever you get for the Fourier Transform corresponds to that frequency.

3. Mar 14, 2010

### jbunniii

The DFT gives you N evenly spaced samples of the DTFT (discrete-time Fourier transform). The frequencies corresponding to these samples are

$$\frac{n}{N} F_s$$

where $n = 0,1,\ldots,N-1$ are the indices of the samples, and $F_s$ is the sampling frequency of the input sequence.