% @(#)scargltsa.hlq 10.3 (ESO-IPG) 7/9/96 09:47:21 %+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %.COPYRIGHT (c) 1992 European Southern Observatory and Warsaw Observatory %.IDENT scargltsa.hlq %.AUTHOR Alex Schwarzenberg-Czerny, ESO and Warsaw Observatory %.KEYWORD MIDAS, help files, SCARGLE/TSA %.LANGUAGE LATEX %.PURPOSE Compute discrete power spectrum %.VERSION 0.0 June 1992 %.RETURNS None %.ENVIRON TSA context %----------------------------------------------------------------------------- \se SECTION./TSA \es\co SCARGLE/TSA 15-SEPT-1992 A.Schwarzenberg-Czerny \oc\su SCARGLE/TSA intab outima start step nsteps Compute Scargle periodogramme for unevenly spaced observations \us\pu Purpose: Compute Scargle periodogramme for unevenly spaced observations by a slow method. This command is recommended for the statistical evaluation of the significance of smooth (sinusoidal) oscillations. Scargle statistics for uncorrelated observations obeys an exponential probability distribution, with expected value of 1. For observations correlated in groups of size 'ncorr', divide value of Scargle statistics by 'ncorr'. For reference see Ap.J. 263, 835. \up\sy Syntax: SCARGLE/TSA intab outima start step nsteps \ys\pa intab = name of input table, it must contain columns :TIME and :VALUE in DOUBLE PRECISION. For numerical reasons it is advisable to subtract mean from :VALUE. \ap\pa outima = name of output image; its first row contains Scargle periodogram and second row contains quality factors. Where factors are small, Scargle periodogram differs from power spectrum considerably. For unit factors Scargle periodogram differs from power spectrum only by its normalization. \ap\pa start = start frequency of the periodogramme, in inverse units of :TIME \ap\pa step = frequency step of the periodogramme, in inverse units of :TIME \ap\pa nsteps = number of frequencies of the periodogramme, in inverse units of :TIME \ap\sa See also: SHOW/TSA, SET/TSA, AOV/TSA, POWER/TSA \as\no Note: By default 'intab', 'outima', 'start', 'step' and 'nsteps' retain their values from the last use of TSA commands, unless explicitly specified. \\ For the detection of signals with sharp features use AOV/TSA instead. \on\exs Examples: \ex SCARGLE/TSA LCURVE PERIODG 0.01 0.01 100 \xe\ex SCARGLE/TSA ? ? 0.2 0.0001 You may run this command after the first example to study the frequency range from 0.2 till 0.21 in more detail. \xe\sxe