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DFT problem

  1. Feb 28, 2012 #1
    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 .
     
  2. jcsd
  3. Feb 29, 2012 #2

    sophiecentaur

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    If your data is all real then why not put the imaginary values as zero?
     
  4. Mar 3, 2012 #3
    then how i get the value of omega for ploting
     
  5. Mar 3, 2012 #4
    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
     
  6. Mar 3, 2012 #5
    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
     
  7. Mar 3, 2012 #6

    sophiecentaur

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    How much do you know about discrete Fourier transforms? What are you trying to find out from the data?
     
  8. Mar 3, 2012 #7
    Thank you for reply. I want to find out a frequency Vs Amplitude graph
     
  9. Mar 3, 2012 #8
    I want to find out time vs Amplitude to frequency vs Amplitude of a signal
     
  10. Mar 3, 2012 #9

    sophiecentaur

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    And what does DFT do? (I want you to work a bit for this. ;-) )
     
  11. Mar 3, 2012 #10
    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.
     
  12. Mar 3, 2012 #11

    sophiecentaur

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    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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