NAME: pdm2 PURPOSE: (one line) Period search by phase dispersion minimization ($\chi^2$ based) DESCRIPTION: This routine computes a Chi^2 statistic for period searching in time-series data loosely based on the technique described by Stellingwerf, ApJ, 224, pp. 953-960 (1978). This algorithm is discused more in Buie and Bus, Icarus, 100, 288-294 (1992) "Physical Observations of (5145) Pholus". CATEGORY: Photometry CALLING SEQUENCE: pdm2,t,x0,sigx0,freq1,freq2,dfreq,freq,period,chi2 INPUTS: t - independent variable (usually time) x0 - dependent variable (usually magnitude or intensity) sigx0 - Uncertainty on x. freq1 - Lower limit to frequency to compute statistic (units=[1/t]) freq2 - Upper limit to frequency to compute statistic (units=[1/t]) dfreq - Frequency interval. (units=[1/t]) OPTIONAL INPUT PARAMETERS: KEYWORD PARAMETERS: NBINS - Number of bins (default = 80) SILENT - Flag, if set, inhibits all printed output. OUTPUTS: freq - Frequency vector. period - inverse frequency. chi2 - Chi^2 statistic. avgyes - Average number of points contained within non-empty bins. nempty - Total number of empty bins. COMMON BLOCKS: SIDE EFFECTS: RESTRICTIONS: PROCEDURE: MODIFICATION HISTORY: Written 1992 Feb 11, by Marc W. Buie, Lowell Observatory 94/08/26 - MWB - added NBINS keyword 94/10/04 - MWB - moved cr to front of print statement (v3.6 bug workaround) 96/07/01 - MWB - added SILENT keyword