Well, I would like to thank you all for your assisstance. I am now progressing and detecting tidal signals in my radon time series.
I really appreciate this. I am not stuck with research now. Rthoughts wrote: > > EDIT: to assist you to assist me in turn, for which I am grateful, more > detail than the below needs to be provided. > > I open tables and view them using Rcmdr so they become active datasets. I > am assuming that x101, x100, etc, are column headings because when the > dataset is edited they can be changed in numerical or non-numerical > values. Lets assume I change those column headings to VB! and V2, and I > would like the output to appear in V3. V2 contains the values to be fft'd. > These are practise values of 24h length sinusoids thus if a sinusoid is > viewed as a frequency value and the time-series are hourly values where > periodicity, not amplitude, counts, this is a 24hr frequency time-series > fo hourly values. > > Here's an example table (to keep it simple, there are 2 columns, V1 for > the 24h frequency values, and V2 for fft output, I don not understand the > fft function enough yet if V1 should contain date/ time values and if V2 > should contain the array, and V3 the output values); > > The table name, I assume, since it appears in the window border and > taskbar, is 'Dataset'. > > V1 V2 > 1 105 > 2 115 > 3 140 > 4 180 > 5 230 > 6 300 > 7 360 > 8 418 > 9 450 > 10 480 > 11 495 > 12 500 > 13 495 > 14 480 > 15 450 > 16 410 > 17 360 > 18 300 > 19 230 > 20 180 > 21 140 > 22 115 > 23 105 > 24 100 > 25 105 > 26 115 > 27 140 > 28 180 > 29 230 > 30 300 > 31 360 > 32 410 > 33 450 > 34 480 > 35 495 > 36 500 > 37 495 > 38 480 > 39 450 > 40 410 > 41 360 > 42 300 > 43 230 > 44 180 > 45 140 > 46 115 > 47 105 > 48 100 > > This is open as a table by view command. How do I go about fft'ing this? > > If I can do this I can then in turn try to analyse my real radon data > which are hourly time-series (thus is a disctrete and periodic array). I > have to analyse it for periodicities that can be attributed to 24hr and > 24.8hr tidal cycles to confirm the substance of the first aim of my > research. > > Secondly, how can I view the output as a graph? I am expecting a frequency > domain from the time domain, thus a frequency of a certain amplitude > should be produced. > > Thank you very much. I hope this clears the matter up a bit. If not, I am > happy to provide more details. > > > > > > Rthoughts wrote: >> >> Dear all, >> >> Before I can get into serious Fourier analysis of Radon time-series I am >> practising with 24hour and 24.8hour sinusoids to assist with my >> interpretation of signals ittributed to tidal input to Radon time series. >> >> I am stuck. I have tried researching this to no avail. I am awating a >> book that should describe fourier transforms in detail and another one >> that should discuss the R application. >> >> I know what the command line is but I can't get it to refer to the array. >> >> What is 'z'? If I have a table open entitled '24hsinusoids' with date/ >> time column by the hour from January 01 2008 00:00 to January 02 2011 >> 00:00 (X01.06.2008) (time column listed as X00:00) with corresponding >> sinudoidal signal value column (X100) to give a complete curve for >> 24hours spread as curves over the whole time-span, how can I fft from >> this table? >> >> fft(z, inverse = FALSE) gives me as; object 'z' not found. >> >> Please help and explain how R recognises the table and does fft's from >> it. The time-series is discrete and periodic (or should be, as I need to >> analyse my Radon time-series fro exactly this and I am very stuck now). >> >> Thank you with all my heart if you can help. >> > > -- View this message in context: http://www.nabble.com/Stuck-with-FFT-tp20192942p20247540.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.
