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DFT problem

by souhal.67
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souhal.67
#1
Feb28-12, 12:27 PM
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 .
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sophiecentaur
#2
Feb29-12, 06:08 AM
Sci Advisor
Thanks
PF Gold
sophiecentaur's Avatar
P: 12,167
If your data is all real then why not put the imaginary values as zero?
souhal.67
#3
Mar3-12, 01:26 AM
P: 7
then how i get the value of omega for ploting

souhal.67
#4
Mar3-12, 01:30 AM
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
souhal.67
#5
Mar3-12, 01:30 AM
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
sophiecentaur
#6
Mar3-12, 03:17 AM
Sci Advisor
Thanks
PF Gold
sophiecentaur's Avatar
P: 12,167
How much do you know about discrete Fourier transforms? What are you trying to find out from the data?
souhal.67
#7
Mar3-12, 03:21 AM
P: 7
Thank you for reply. I want to find out a frequency Vs Amplitude graph
souhal.67
#8
Mar3-12, 03:23 AM
P: 7
I want to find out time vs Amplitude to frequency vs Amplitude of a signal
sophiecentaur
#9
Mar3-12, 03:24 AM
Sci Advisor
Thanks
PF Gold
sophiecentaur's Avatar
P: 12,167
And what does DFT do? (I want you to work a bit for this. ;-) )
souhal.67
#10
Mar3-12, 03:31 AM
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.
sophiecentaur
#11
Mar3-12, 03:40 AM
Sci Advisor
Thanks
PF Gold
sophiecentaur's Avatar
P: 12,167
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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