########### splitndgrid ###########

    Program to read an ASCII list of scattered points in nD space and bin 
    them into files representing bins on an N-dimesional cartesian grid. A 
    border may defined around each bin, where border width is constant for 
    each dimension. Borders of adjacent bins may overlap so that points may
    be binned into more than one bin.
    
    Usage:
        
        splitndgrid INFILE OUTPATH NDIMS MINS MAXS BINSIZE BORDERSIZE
                
    Arguments:
        
        INFILE - Path to the ASCII source file containing the points. Each
                 record must be formatted: D1 D2...DN\\n  where e.g. D1 is
                 the position of the point in dimension 1. Note that fields
                 are whitespace separated and each record is terminated with
                 a newline character.
        
        OUTPATH - The output path. Output file names for each bin on the 
                  grid are made by suffixing OUTPATH with a string made of
                  underscore-separated bin numbers (which start at 0).
        
        NDIMS   - The number of dimensions, the first n fields to
                  read from each line in INFILE that describe the location
                  of the point.
        
        MINS    - Comma separated string containing the minimum values of the
                  grid to bin onto for dimensions 1..n.
                  
        MAXS    - Comma separated string containing the maximum values of the
                  grid to bin onto for dimensions 1..n.
        
        BINSIZE - Comma separated string containing the bin widths for each
                  dimension.
        
        BORDERSIZE - Comma separated string containing the border widths for 
                     each dimension.
        
    Example:
        
        To bin a list of points on a lat lon grid where each record contains
        the fields:
            LAT LON ALTITUDE
        
        We only want to bin the records into 5x5 degree lat lon bins. The 
        altitude field is propagated into the binned files. We assign no
        border in the longitude direction, but one of 0.02 degrees in the 
        latitude direction.
        
        splitndgrid globalelev.txt ~/elevbins/bin_ 2 -90,0 90,360 5,5 0.02,0
        
        Note that points may be in more than one bin in the latitude 
        direction, because the 0.02 degree borders of adjacent bins overlap
        in that dimension.
        
        This example will produce 2592 files from:
                ~/elevbins/bin_01_01.txt
            to:
                ~/elevbins/bin_36_72.txt
            
    Author: Elliot Sefton-Nash  (e.sefton-nash@uclmail.net)  
    
    Changelog: 
        2014-01-13 Original