rndpwrlc

          Simulate a light-curve with a power-law distributed
          periodogram

          light curve simulation

          rndpwrlc,time,rate,nt=nt,beta=beta,sigma=sigma,mean=mea

          -

          nt: Number of bins of the simulated lightcurve (default:65536)
              Should be power of two for optimum performance (FFT...)
        beta: Power law index of the periodogram (default: 1.5)
        mean: Mean count rate of the simulated lightcurve (default: 0.)
       sigma: Standard deviation of the lightcurve to be simulated
              (default:1.)
        seed: Seed for the random number generator (returned if not
              defined -- see IDL help for randomu function)

        randomu: if set, the IDL random number generator is used. If
                not set, ran2 (from aitlib) procedure is used.

        time: Time array (trivial :-) )
        rate: Array of countrates of length n

        seed: see above

        There are rumors that the IDL random number generator is not
        absolutely perfect -- in fact, we have seen this in our
        simulations of deadtime noise. So the periodogram has not
        perfectly independent bins. For high precision work use one
        of the rngs implemented by Sara Benlloch, ran2_normal, and
        part of aitlib.

        Simulation of the fourier transform of the light curve, and
        inverse Fourier transform. See
        J. Timmer & M. Koenig, On generating power law noise, A&A,
        300, 707-710, 1995
        for details
        RAN2_NORMAL (aitlib)

        rndpwrlc,ti,lc,mean=80.,sigma=10.,seed=seed
        psd,ti,lc,freq,psd
        plot,freq,psd,/xlog,/ylog

        Based on code by M. Koenig and J. Timmer, dated 1996 April 17
        Version 1.0: J. Wilms, K. Pottschmidt, IAAT, 2000 October 26
        Version 1.1; S. Benlloch, IAAT, 2000 November 28
                 keyword randomu added
                 ran2_normal implemented
        Version 1.2; S. Benlloch, IAAT, 2001 June
                 corrected error in beta and treatment of fourier transform
        Version 1.3; S. Benlloch, IAAT 2002 January
                 corrected error by odd nt
 $Log: rndpwrlc.pro,v $
 Revision 1.6  2002/09/12 09:59:22  wilms
 added automatic CVS logging

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