Help diagnose diseases

Compare Multiple Programs





======================================================================================================================== 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-tp20192942p20204314.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-h ... @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.