[Help-gsl] About FFT

[Daniel de Oliveira Pereira]

Hi. Im trying to use the FFT to do a filter for my signals. They dont have
a fixed length but isnt also a real-time filtering.

I understand the concept of frequency domain but what i dont get is how can
i determine for each increment what frequency im supose to get. For an
example, i have 5000 samples of a heartbeat signal at 250hz sample
frequency. Im supose to have a 5000 size variable but for each increment,
what frequency it should be? The n=0 is f=0? And for n=1? the frequency
would be 1hz? Or should be (250/5000)*(1)? Or its another formula?

May be a little confuse text due my bad english, but i did my best.

Regards,
Daniel