Hi,
I have more questions about the fft. The application in Excel is very limited. In Excel I can adjust graphs and calibrate the x and y-axis. The input and process, however, is limited compared to R. With a Dataset table where one column is the hour difference and the second are the values with hidden frequencies, how is it possible to plot a frequency spectrum with the x-axis calibrated to the hour difference where the left should be infinite frequency and half way to the right should be the midpoint. Below is an example dataset with a 24 hour sinusoid that I would like to fft for assisting with my ability to interpret my output. How do I calibrate the plot so that the x-axis displays the cycles per that run and the y-axis is frequency? In the command line, (Dataset$X10, inverse = FALSE, frequency = 24), what does the frequency line specify and and it is related to number of data points? By doing this am I generating frequencies rather than revealing them? Secondly, how to do generate a spectrogram on R? I believe that this one is where the x-axis is the cycles per data point with the left being infinite cycles to 0.5 being one cylce per 2 data points and the y-axis is the amplitude. Thank you very much in advance if you can help and share your experience/ knowledge. I am progressing with fourier transforms in my research but I am new to it so that doesn't help. Thirdly, I came across in my reading that it is a good idea to generate a correlogram to determine if it is valid to do an fft on the dataset. How would I go about doing this and how is frequency/ lag determined? 00/01 00:00 4.330 00/01 01:00 3.536 00/01 02:00 2.500 00/01 03:00 1.294 00/01 04:00 0.000 00/01 05:00 -1.294 00/01 06:00 -2.500 00/01 07:00 -3.536 00/01 08:00 -4.330 00/01 09:00 -4.830 00/01 10:00 -5.000 00/01 11:00 -4.830 00/01 12:00 -4.330 00/01 13:00 -3.536 00/01 14:00 -2.500 00/01 15:00 -1.294 00/01 16:00 0.000 00/01 17:00 1.294 00/01 18:00 2.500 00/01 19:00 3.536 00/01 20:00 4.330 00/01 21:00 4.830 00/01 22:00 5.000 00/01 23:00 4.830 01/01 00:00 4.330 01/01 01:00 3.536 01/01 02:00 2.500 01/01 03:00 1.294 01/01 04:00 0.000 01/01 05:00 -1.294 01/01 06:00 -2.500 01/01 07:00 -3.536 01/01 08:00 -4.330 01/01 09:00 -4.830 01/01 10:00 -5.000 01/01 11:00 -4.830 01/01 12:00 -4.330 01/01 13:00 -3.536 01/01 14:00 -2.500 01/01 15:00 -1.294 01/01 16:00 0.000 01/01 17:00 1.294 01/01 18:00 2.500 01/01 19:00 3.536 01/01 20:00 4.330 01/01 21:00 4.830 01/01 22:00 5.000 01/01 23:00 4.830 02/01 00:00 4.330 02/01 01:00 3.536 02/01 02:00 2.500 02/01 03:00 1.294 02/01 04:00 0.000 02/01 05:00 -1.294 02/01 06:00 -2.500 02/01 07:00 -3.536 02/01 08:00 -4.330 02/01 09:00 -4.830 02/01 10:00 -5.000 02/01 11:00 -4.830 02/01 12:00 -4.330 02/01 13:00 -3.536 02/01 14:00 -2.500 02/01 15:00 -1.294 02/01 16:00 0.000 02/01 17:00 1.294 02/01 18:00 2.500 02/01 19:00 3.536 02/01 20:00 4.330 02/01 21:00 4.830 02/01 22:00 5.000 02/01 23:00 4.830 03/01 00:00 4.330 03/01 01:00 3.536 03/01 02:00 2.500 03/01 03:00 1.294 03/01 04:00 0.000 03/01 05:00 -1.294 03/01 06:00 -2.500 03/01 07:00 -3.536 03/01 08:00 -4.330 03/01 09:00 -4.830 03/01 10:00 -5.000 03/01 11:00 -4.830 03/01 12:00 -4.330 03/01 13:00 -3.536 03/01 14:00 -2.500 03/01 15:00 -1.294 03/01 16:00 0.000 03/01 17:00 1.294 03/01 18:00 2.500 03/01 19:00 3.536 03/01 20:00 4.330 03/01 21:00 4.830 03/01 22:00 5.000 03/01 23:00 4.830 -- View this message in context: http://www.nabble.com/Stuck-with-FFT-tp20192942p20556317.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.
