Question about FFT

hello to all

supposed that i have a matrix of 10 values [1x10]

and i want to sample it by IFFT to get 1000 samples ,i get a matrix of [1x1000]

and when i want to receive the same 10 values back by FFT

im getting a matrix of [1x1000] ,how do i get the 10 original values back ???

thank alot

Answer 1

[Honglei Chen]

Hi itsik,

When you do IFFT to get 1000 samples, it simply pads zero at the end. So when you do fft back, just take the first 10 samples.

x = rand(1,10);
y = fft(ifft(x,1000));
[x;y(1:10)]

HTH,

Honglei

Answer 2

[Saee]

I have a vector of discrete data( they show the positions in single time), I am using fft to see how this data behaves in terms of periodicity? all example I found in matlab talk about the sample frequency and sample length , I know that the sample length can be the length of my vector ,but how the sample frequency plays role here ? will you please give me some helps by answering my question?