MagicPlot Manual

Plotting and nonlinear fitting software

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Table of Contents

Fast Fourier Transform (FFT)

Open table with initial data and use Analysis → Fast Fourier Transform menu item to perform FFT.


MagicPlot uses 'electrical engineering' convention to set the sign of the exponential phase factor of FFT. 1)

Here c_n is signal components and C_n spectrum components, n = 1...N.

Check Box
Forward Transform
Inverse Transform
Unchecked C_n = sum{k=1}{N}{c_k e^{−2 pi i k n {/} N}} c_n = 1/N sum{k=1}{N}{C_k e^{2 pi i k n {/} N}}
Checked C_n = 1/N sum{k=1}{N}{c_k e^{−2 pi i k n {/} N}} c_n = sum{k=1}{N}{C_k e^{2 pi i k n {/} N}}


Sampling Interval Sampling interval dt is used to compute the data in resulting sampling column which will be
(if Center zero frequency is unchecked): 0,~ 1/{dt N},~ 2/{dt N},~ ... ~{N−1}/{dt N}
Columns with real and imaginary components of data.
If your data is only real, select <all zeros> imaginary item
Transform direction
Normalize forward transform Divide forward transform result by number of points N
Center zero frequency If selected, after forward Fourier transform the two parts of spectrum will be rearranged so that the lower frequency components are in the center; the opposite rearrangement of spectrum will be done before inverse transform if any.
Most scientific applications uses the same sign conventions. But note, that the sign of exponential phase factor in Numerical Receipts in C, 2nd edition, p. 503 is the opposite
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fft.1272230713.txt.gz · Last modified: Sun Nov 8 12:20:32 2015 (external edit)