Auto Correlation Function slow method (Application).
Application acf calculates the auto correlation function of a time series by using a slow algorithm. It requires one input series. It is run in the Question/Answer user interface by typing:
[n]Xronos> acsin the Partial Question/Answer user interface by typing:
[n]Xronos> acs [series1]and in the Command-Driven user interface by typing:
[n]Xronos> acs[/qualifier1/qual2/... etc] [series1]
The newbin time must correspond to an integer multiple of the maximum bin time. The default newbin time is either the maximum bin time (if fewer than 512 newbins are expected) or the integer multiple of it which gives a single interval with 512 newbins at most. The average count rate in each interval is subtracted from all newbins, and gaps and rejected newbins are replaced with zeroes, before the auto correlation function is calculated.
The auto correlation error bars are obtained either by propagating the theoretical errors bars of the autocorrelations from individual intervals (in turn obtained by propagating the newbin error bars through the autocorrelation formula) or by evaluating directly the standard deviation of the average of the autocorrelations in each delay bin from different intervals. This depends on whether the specified number of intervals per frame is, respectively, smaller or larger than the value of global parameter number 9. (default =5). Error bars are plotted by default.
The effects introduced by windows, data gaps etc. can be studied by analysing the exposure profile of the time series, by setting global parameter number 10 to 1.
The analysis normalisation flag, specified by global parameter number 11 has the same meaning as in application acf.