# Determining the full DFT values of X(k) given a partial sample [closed]

I have a sample of a signal lets say 8 values of a 16 value sequence. I am trying to obtain the full DFT from the partial.

I am thinking that I am going to work back, I read the matlab documentation and have come acrosss an inverse function. Am I on the right track? I was not able to see a pattern in the results..

yt = [5 2-5i -11.8 + 1.8i 12.85 +1.2i -1-3.4i 0.5-0.866i 6-1.9i 12.8+5i];
ifft(yt);
Xsym = ifft(yt,'symmetric')

Xsym =

1.2333   -0.7580    2.7979    5.5777   -2.3988   -4.1984    3.4223    0.5402   -1.2162


If I am not on the right track what should I be looking at?

• I am not sure I follow---if you have a signal of 8 time domain values, the DFT will have 8 frequency domain values, given as fft(yt). What does partial mean? ifft will then recover the time domain values back from the frequency domain values. Feb 22 at 6:33
• The signal has a total of 16 real values, I am required to determine the remaining 8 given these first 8 values. I used the word partial as 8 values are a partial sample of a 16 value sequence.
– Tam
Feb 22 at 6:45
• The values you're showing (assuming it's yt?) aren't real, they're complex. If that's the first 8 values of a DFT sequence, and you're asked to find the remaining 8, and you know the input is a real sequence, I suggest you learn about the properties of the DFT for real-valued sequences (specifically, conjugate symmetry). If I'm missing the point, then that means your question is still un-clear and you should edit it with more precise information on your problem.
– Jdip
Feb 22 at 7:07