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## Taking an IFFT of discrete numbers

Asked by Hande

### Hande (view profile)

on 11 Dec 2012
Accepted Answer by Honglei Chen

### Honglei Chen (view profile)

I have a set of values, power(W) versus frequency. First i transformed the Watt values to dBm, after i need to take the ifft for passing the time domain. More clearly, in 'freq' variable there is a frequency values from 0 Hz to 10000Hz. In 'data' variable, there is a power values corresponds to the frequency values. When I do ifft(data); , I dont use any frequency values, and It is meaningless. I know that for idft, the point number is important but how can I do this transform with the frequency values ?

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## 1 Answer

### Honglei Chen (view profile)

Answer by Honglei Chen

### Honglei Chen (view profile)

on 11 Dec 2012
Accepted Answer

Not sure if I understand your question correctly but just talking about IFFT operation itself, it has nothing to do with the frequency value. FFT and IFFT are just mathematical operations. The frequency value is what you use to interpret the data and gave them some physical meanings

Hande

### Hande (view profile)

on 12 Dec 2012

I understand what you mean, so I changed my question. When I take an IFFT of the data, the result is complex values and when I take FFT again, the result is not same with the original values. Probably It is because of complex values. How can I solve it ?

Honglei Chen

### Honglei Chen (view profile)

on 12 Dec 2012

Could you share an example?

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