SCARGLE/TSA                            15-SEPT-1992 A.Schwarzenberg-Czerny
    
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.
Syntax:
           SCARGLE/TSA intab outima start step nsteps
           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.
           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.  
           start =  start frequency of the periodogramme, in inverse
                    units of :TIME 
           step  =  frequency step of the periodogramme, in inverse
                    units of :TIME 
           nsteps = number of frequencies of the periodogramme, in inverse
                    units of :TIME 
See also:
           SHOW/TSA, SET/TSA, AOV/TSA, POWER/TSA
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. 
Examples:
           SCARGLE/TSA LCURVE PERIODG 0.01 0.01 100 
           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.