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*Subject*: Re: Complex -> Real FFT*From*: Jeff Wasserman <wasserman(at)ll.mit.edu>*Date*: Mon, 26 Jul 1999 22:00:00 -0400*Newsgroups*: comp.lang.idl-pvwave*Organization*: MIT Lincoln Laboratory*References*: <7nf5s2$4pl$1@cnn.Princeton.EDU> <MPG.1205214feadb8167989849@news.frii.com>*Reply-To*: nospam(at)ll.mit.edu*Xref*: news.doit.wisc.edu comp.lang.idl-pvwave:15842

David Fanning wrote: > > Jeremy Kepner (jvkepner@muse.Princeton.EDU) writes: > > > Does anyone know of a Complex to Real FFT that has > > been implemented in IDL. (Likewise a corresponding > > Real to Complex FFT would also be nice). > > I'm probably missing something deep here, but > doesn't this do what you want? > > result = FLoat(complex_fft_expression) > result = Imaginary(complex_fft_expression) If you don't care about phase information with your FFT data, and instead want just an absolute power measurement (like a spectrum analyzer), you could use power_spectrum = Abs(complex_fft_data) [the abs function returns the value of sqrt(real^2+imaginary^2) if it's argument is complex] Conversely, you could also get the phase info into an array phase_array = Tan(complex_fft_data) [The tan function also nicely works with complex data] >From these two arrays you could then go back to the complex array. However, as far as I know, there is no way to obtain the two independent variables of the original complex array after it's been converted to reals. ------------------------------------------------------------ Jeffrey Wasserman - Member of Technical Staff Group 83 Electro-Optical Materials and Devices MIT Lincoln Laboratory Lexington, MA ------------------------------------------------------------ Warning - I am using a government mail server, any un- authorized spam mail will be prosecuted! Change the x's to dots and the y to 'at' sign to respond: wassermanyllxmitxedu ------------------------------------------------------------

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