Extracting periodicity with Fast Fourier Transform

[Ebert87]

Hello all,

I want to extract the period out of a complex discrete signal.

Currently I have the Matlabscript of the attachement.

However, the values I get out of this script are not correct. There is some kind of systematic bias in it.

I think it has something to do with index * samplefrequency.

Anyone an idea what could be wrong?

Thanks in advance!

 

[Hassan2]

Right, you should divide by sample frequency. Period and frequency have inverse relation.

 

[Ebert87]

Right, you should divide by sample frequency. Period and frequency have inverse relation.

Thanks, I tried it, but now the values are extremely big. Maybe I am using the y-axis value of the frequency domain graph, instead of the x-axis value (which says something about thefrequency of the original signal, right?)?

Getting confused now

 

[Hassan2]

What are the values of index and Samplefreq?

I think you should use this:

Period=(Length of the sequence)*dt/index