From help-octave-request at bevo dot che dot wisc dot edu Fri Jan 18 12:33:18 2002 Subject: On "cleaning" residual values from complex matrices From: Roberto Hernandez To: help-octave at bevo dot che dot wisc dot edu Date: Fri, 18 Jan 2002 15:31:43 -0300 Hello everyone, I've been doing a lot of processing with FFT. While the magnitude of the results I've been getting makes perfect sense, I noticed the phase was totally incongruent. After looking into the problem, I realized it boils down to residual values. What's happening is that values that should be zero show up as something like +/-eps +/-eps*i, so that throws off any phase calculations. Is there any function that "cleans" residual values (makes them zero)? I looked up "precision" in the help files and found information on the built in variables 'realmin', 'realmax' and 'eps'. However, I found no "cleaning" functions. If it's not available, I don't have a problem with writing my own. I'm not an expert in numerical analysis, so I figure it's very likely that I'll overlook something. My idea is to check for values where the real/imaginary part is <= 'eps' and truncating the real/imaginary part for those values to zero. If there is already a function that does this, please let me know. Otherwise, if I do have to write my own, is there anything else the function should do besides what I already mentioned? TIA, Roberto ------------------------------------------------------------- Octave is freely available under the terms of the GNU GPL. Octave's home on the web: http://www.octave.org How to fund new projects: http://www.octave.org/funding.html Subscription information: http://www.octave.org/archive.html -------------------------------------------------------------