Hi, I'm in dire need of a fast fourier transformation for me stupid biologist, i.e. I have a heartbeat signal and would like to decompose it into pure sin waves, getting three vectors, one containing the frequencies of the sin waves, one the magnitudes and one the phases (that's what I get from my data acquisition software's FFT function). I'd be very much obliged, if someone could point out which command would do the job in R. Thanks! Wolfgang
FFT, frequs, magnitudes, phases
3 messages · Wolfgang Waser, Peter Dalgaard, Martin Maechler
Wolfgang Waser <wolfgang.waser at rz.hu-berlin.de> writes:
Hi, I'm in dire need of a fast fourier transformation for me stupid biologist, i.e. I have a heartbeat signal and would like to decompose it into pure sin waves, getting three vectors, one containing the frequencies of the sin waves, one the magnitudes and one the phases (that's what I get from my data acquisition software's FFT function). I'd be very much obliged, if someone could point out which command would do the job in R.
fft(), but notice that it gives the complex transform. You need to do a little homework to get at the magnitude/phase values. (Basically, you just have to take Mod() and Arg(), but there some conventions about the frequencies and multipliers that one can get wrong).
O__ ---- Peter Dalgaard ??ster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
1 day later
"PD" == Peter Dalgaard <p.dalgaard at biostat.ku.dk>
on 19 Aug 2005 14:16:42 +0200 writes:
PD> Wolfgang Waser <wolfgang.waser at rz.hu-berlin.de> writes:
>> Hi,
>>
>> I'm in dire need of a fast fourier transformation for me
>> stupid biologist, i.e. I have a heartbeat signal and
>> would like to decompose it into pure sin waves, getting
>> three vectors, one containing the frequencies of the sin
>> waves, one the magnitudes and one the phases (that's what
>> I get from my data acquisition software's FFT function).
>> I'd be very much obliged, if someone could point out
>> which command would do the job in R.
PD> fft(), but notice that it gives the complex
PD> transform. You need to do a little homework to get at
PD> the magnitude/phase values. (Basically, you just have to
PD> take Mod() and Arg(), but there some conventions about
PD> the frequencies and multipliers that one can get wrong).
Once you've finished the "homework", others might be interested
in your result... so it will be found in the future using
RSiteSearch().
Martin