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Required Reading


   CSPICE_EKGI returns an element of integer data from a 
   specified row in a specified column of the set of rows matching 
   the previous cspice_ekfind SELECT query.

   For important details concerning this module's function, please refer to
   the CSPICE routine ekgi_c.


      selidx   the scalar integer index for a column of interest
               satisfying the SELECT clause, the column indices
               range from 0 to N-1 where N equals the total number
               of columns satisfying the SELECT clause.
      row      the scalar integer index for a row in the column
               identified by 'selidx', the column indices
               range from 0 to M-1 where M equals the total number
               of rows satisfying the SELECT clause.
      elment   the scalar integer index for a element of 
               the data at the 'selidx','row' position; a scalar
               value at 'selidx','row' has 'elment' value zero.
   the call:
      cspice_ekgi, selidx, row, elment, idata, null, found
      idata    the integer value of the requested element at
               data location 'selidx', 'row', 'elment'.
      null     a scalar boolean indicating if the 'idata' has a null value.
      found    a scalar boolean indicating whether the specified 
               value at 'selidx', 'row', 'elment' was found.


   Any numerical results shown for this example may differ between
   platforms as the results depend on the SPICE kernels used as input
   and the machine specific arithmetic implementation.

      ;; Assign an EK file to load.
      EK     = 'test_file.ek'
      ;; Load the EK.
      cspice_furnsh, EK
      ;; Assume the file test_file.ek contains the table 'scalar_2',
      ;; and that "scalar_2' has the column named 'i_col_1' of integer
      ;; values.
      ;; Define a set of constraints to perform a query on all
      ;; loaded EK file (the SELECT clause). In this case select 
      ;; the column "i_col_1" from table "scalar_2."
      query = "Select i_col_1 from scalar_2 order by row_no"
      ;; Query the EK system for data rows matching the
      ;; SELECT restraints.
      cspice_ekfind, query, nmrows, error, errmsg
      ;; Check whether an error occurred while processing the
      ;; SELECT clause. If so, output the error message.
      if ( error ) then begin
         print, 'SELECT clause error: ', errmsg
      ;; Loop over each row found to match the query.
      for rowno = 0, (nmrows-1) do begin
         ;; Fetch the integer data. We know the query returned
         ;; one column and the column contains only scalar data, 
         ;; so the index of all elements is 0.
         selidx = 0
         eltidx = 0
         ;; Use cspice_ekgi to retrieve the integer from 
         ;; row/column position.
         cspice_ekgi, selidx, rowno, eltidx, idata, isnull, found
         ;; Output the value, if non-null data exists at the 
         ;; requested position.
         if ( NOT isnull ) then begin
            print, 'Integer data: ', idata
      ;; Unload the EK. Note, you don't normally unload an EK
      ;; after a query, rather at the end of a program.
      cspice_unload, EK
   IDL outputs:
      Integer data:      2000001
      Integer data:      2000002
      Integer data:      2000003
      Integer data:      2000004
      Integer data:      2000005
      Integer data:      2000006
      Integer data:      2000007
      Integer data:      2000008
      Integer data:      2000009
      Integer data:      2000010
      Integer data:      2000011
      Integer data:      2000012
      Integer data:      2000013
      Integer data:      2000014
      Integer data:      2000015
      Integer data:      2000016
      Integer data:      2000017
      Integer data:      2000018
      Integer data:      2000019
      Integer data:      2000020


   If a SELECT clause returns data consisting of three 
   columns (N=3) and four rows (M=4),

              col 0    col 1    col 2
      row 0   val_00   val_01   val_02 
      row 1   val_10   val_11   val_12
      row 2   val_20   val_21   val_22
      row 3   val_30   val_31   val_32
   with "col 1" and "col 2" containing integer data
   and the "val_31" a vector of K integers, the data position
   relates to the data:
   fetch scalar "val_21"
      'selidx' = 1, 'row' = 2, 'elment' = 0
   fetch scalar "val_32"
      'selidx' = 2, 'row' = 3, 'elment' = 0
   fetch the final element of vector "val_31"
      'selidx' = 1, 'row' = 3, 'elment' = K-1
   'elment' is allowed to exceed the number of elements in 
   the column entry; if it does, 'found' returns
   as SPICEFALSE.  This allows the caller to read data 
   from the column entry in a loop without checking the 
   number of available elements first.

Required Reading



   -Icy Version 1.0.1, 24-JAN-2010, EDW (JPL)

      Corrected errors in the description of the indices behavior
      as given in 'elment' argument. That description is now
      in the "Particulars" section.

   -Icy Version 1.0.0, 16-JUN-2003, EDW (JPL)


   fetch element from integer column entry 

Wed Apr  5 17:58:00 2017