4.92 sddssampledist

• description: sddssampledist provides for pseudo-random sampling of probability distributions. It also provides nonrandom sampling using Halton sequences.
• examples: Draw random samples from a normal (Gaussian) distribution, G(z), shifted to have a sigma of 10 and centroid of 5.
      sddssampledist gaussian.sdds samples.sdds -samples=100 -columns=indep=z,df=G,output=zSample,factor=10,offset=5  
      

• synopsis:
      sddssampledist [input] [output] [-pipe=[in][,out]]  
        -columns=independentVariable=name,{cdf=CDFName | df=DFName}  
          [,output=name][,units=string][,factor=value]  
          [,offset=value][,datafile=filename]  
          [,haltonRadix=primeNumber[,randomize[,group=groupID]]]  
        [-columns=...] [-samples=integer] [-seed=integer] [-threads=number]  
      

• files: input is the default input file for distribution functions (DFs) and cumulative distribution functions (CDFs). input is not required if all -columns options give the datafile qualifier. output contains the samples. By default the sampled data names match the independent variable names from the -columns options. Use the output qualifier to change these names.
• switches:
  • -pipe[=input][,output] — The standard SDDS Toolkit pipe option.
  • -columns=independentVariable=name,{cdf=CDFName | df=DFName}[,output=name][,units=string][,factor=value][,offset=value][,datafile=filename][,haltonRadix=primeNumber[,randomize[,group=groupID]]]— Specifies the CDF or DF from which to draw samples (cdf or df qualifier) and the independent variable. This option may be given multiple times. output sets the column name for the samples. units specifies the units. factor and offset apply a transformation x → x*f +o. datafile gives an alternate file containing the distribution function data, otherwise the main input file is used. haltonRadix selects the radix for generating a non-random Halton sequence, which provides smoother sampling than a pseudo-random sequence. The radix should be a small prime number. Use randomize to remove correlations when using the same radix for multiple sequences. Use group to assign options to a group for correlated randomization.
  • -samples=integer — Specifies the number of samples to generate.
  • -seed=integer — Specifies the seed for the random number generation. Should be a large, odd integer. If not given, the system clock is used.
  • -threads=number — Specifies the number of datafile distributions to read concurrently. The default is 1. Sampling and SDDS output operations are performed serially, preserving seeded output order.
• author: M. Borland, ANL/APS.