scriptfilename := 'make_scan_index.g';
#=============================================================================
#
# Set values in the scan_number column in MS.  
#
# This script only recognizes a new scan when a field_id or a 
# subarray_id changes. I haven't quite figured out how to use the 
# data_desc_id yet...
#
#-----------------------------------------------------------------------------
#  Set some input control parameters here :
#
   inname  := 'ab973short';
#
#=============================================================================
#
include 'logger.g';
include 'table.g';
#
# Build the input and output file names.
#
   msfilename   := spaste(inname, ".ms");
#
   tbl := table(msfilename, readonly=F);
#
   scan_num:=tbl.getcol('SCAN_NUMBER');
   field_id:=tbl.getcol('FIELD_ID');
   data_id :=tbl.getcol('DATA_DESC_ID');
   subarray:=tbl.getcol('ARRAY_ID');
#
   nrows := len(scan_num);
#
   last_scan_num :=  0;
   last_field_id := -1;
   last_data_id  := -1;
   last_subarray := -1;
#
   print "nrows = ", nrows;
   for (irow in 1:nrows)
   {
       if (last_field_id != field_id[irow] ||
           last_subarray != subarray[irow])
       {
           last_scan_num := last_scan_num + 1;
           last_field_id := field_id[irow];
           last_data_id  := data_id[irow];
           last_subarray := subarray[irow];
           print irow, 'new : ', last_scan_num, last_field_id, last_data_id, last_subarray;
       }

       scan_num[irow] := last_scan_num;
   }
#
   ok := tbl.putcol ('SCAN_NUMBER', scan_num);
#
   ok := tbl.done();
#