You need to decide how you are going to interpolate the values. Look at the zoo package- na.approx() . spectrum() take the x axis and produces a power spectrum vs. cycles/time. you may interpret this however it makes ssnse- if it makes sense.
On Mon, Nov 3, 2008 at 4:23 AM, Claudia Beleites <[EMAIL PROTECTED]> wrote: > Dear all, > > I work with (vibrational) spectra: some kind of intensity (I) over frequency > (nu), wavelength or the like. > I want to do fourier transform for interpolation, smoothing, etc. > > My problem is that the spectra are often irregularly spaced in nu: the > difference between 2 neighbouring nu varies across the spectrum, and data > points may be missing. > > Searching for discrete fourier transform I found lots of information and > functions - but I didn't see anything that just works with irregularly spaced > signals: all functions I found take only the signal, not its x-axis. > > Where should I look? > Or am I lacking some math that tells how to do without the frequency axis? > > Thanks a lot for your help, > > Claudia > > > -- > Claudia Beleites > Dipartimento dei Materiali e delle Risorse Naturali > Università degli Studi di Trieste > Via Alfonso Valerio 6/a > I-34127 Trieste > > phone: +39 (0 40) 5 58-34 47 > email: [EMAIL PROTECTED] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Stephen Sefick Research Scientist Southeastern Natural Sciences Academy Let's not spend our time and resources thinking about things that are so little or so large that all they really do for us is puff us up and make us feel like gods. We are mammals, and have not exhausted the annoying little problems of being mammals. -K. Mullis ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
