# DFT problem

by souhal.67
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 P: 7 I have a f(n*t) vs t data areay how to find out its (DFT) fourier transform in c. I find every time that every program needs its real and imaginarry part. but i have only magnitude. please help me out to find DFT of these data .
 Sci Advisor Thanks PF Gold P: 12,238 If your data is all real then why not put the imaginary values as zero?
 P: 7 then how i get the value of omega for ploting
 P: 7 DFT problem after sampling I have value of t & X(t) like 375.020000 -0.754661 375.030000 -0.755227 375.040000 -0.755841 375.050000 -0.756501 375.060000 -0.757207 375.070000 -0.757960 375.080000 -0.758759 375.090000 -0.759604 375.100000 -0.760494 375.110000 -0.761431 375.120000 -0.762414 375.130000 -0.763442 375.140000 -0.764515 375.150000 -0.765633 375.160000 -0.766797 375.170000 -0.768005 375.180000 -0.769258 I would like to find DFT and I need omega/freq and X(W) value please help me Thank you
 P: 7 after sampling I have value of t & X(t) like 375.020000 -0.754661 375.030000 -0.755227 375.040000 -0.755841 375.050000 -0.756501 375.060000 -0.757207 375.070000 -0.757960 375.080000 -0.758759 375.090000 -0.759604 375.100000 -0.760494 375.110000 -0.761431 375.120000 -0.762414 375.130000 -0.763442 375.140000 -0.764515 375.150000 -0.765633 375.160000 -0.766797 375.170000 -0.768005 375.180000 -0.769258 I would like to find DFT and I need omega/freq and X(W) value please help me Thank you
 Sci Advisor Thanks PF Gold P: 12,238 How much do you know about discrete Fourier transforms? What are you trying to find out from the data?
 P: 7 Thank you for reply. I want to find out a frequency Vs Amplitude graph
 P: 7 I want to find out time vs Amplitude to frequency vs Amplitude of a signal
 Sci Advisor Thanks PF Gold P: 12,238 And what does DFT do? (I want you to work a bit for this. ;-) )
 P: 7 I have a collage project and I have a system out put I must make a program to find out system's frequency response of numerically.
 Sci Advisor Thanks PF Gold P: 12,238 You didn't say what the DFT does. You have asked a question that suggests you have no idea. I could tell you anything and you would believe me. You need to understand about the process. If you want an answer then put some data in for a familiar waveform for which you know the frequency spectrum. Try some sine waves with different periods.

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