RANDSUBSET Select a random subset of samples

    SUB=RANDSUBSET(DATA,PAR)
    [SUB,REST,IND1,IND2]=RANDSUBSET(DATA,PAR,options)

    SUB=RANDSUBSET(DATA,PROP,PAR) % sample the property PROP

 INPUT
    DATA      Data set
    PAR       Selection parameter (scalar or vector)
               01       Number of samples per class
    PROP      Name of property to sample (default: 'lab')

 OUTPUT
    SUB       Selected subset
    REST      Remainder of the DATA
    IND1,IND2 Indices of the samples in SUB and REST

 OPTIONS
    'all'     Select the subset from a complete data set
    'atmax'   Take at maximum the specified number of samples

 DESCRIPTION
 RANDSUBSET selects a random subset of samples in DATA. The Selection is
 performed per-class by default. If PAR is a vector, it specifies
 selection for each class separately (zero entries are supported).  To
 select fraction or number of samples from the complete data set,
 add 'all' option:
   SUB=RANDSUBSET(DATA,PAR,'all')
 If property name PROP is specified, RANDSUBSET works on this property.
 For example, to select random 100 samples per-patient, use:
   SUB=RANDSUBSET(DATA,'patient',100)
 Note that the PROP property must be indexed (SDLAB object).
 To make sure the subset SUB does not contain more than M samples, use
 the 'atmax' option.