Procedure

   wnfltd_c ( Filter small intervals from a DP window ) 

   void wnfltd_c ( SpiceDouble     smlint,
                   SpiceCell    *  window )

Abstract

   Filter (remove) small intervals from a double precision window.

Required_Reading

   WINDOWS

Keywords

   WINDOWS

Brief_I/O

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
   smlint     I   Limiting measure of small intervals.
   window    I-O  Window to be filtered.

Detailed_Input

   smlint      is the limiting measure of the small intervals to be
               filtered. Intervals of measure less than or equal to
               `smlint' are removed from the window. The measure `smlint' is
               signed, and is used as is---the absolute value of `smlint'
               is not used for in place of negative input values.

   window      on input, is a window containing zero or more
               intervals.

               `window' must be declared as a double precision SpiceCell.

               CSPICE provides the following macro, which declares and
               initializes the cell

                  SPICEDOUBLE_CELL        ( window, WINDOWSZ );

               where WINDOWSZ is the maximum capacity of `window'.

Detailed_Output

   window      on output, is the original window, after small
               intervals have been removed.

Parameters

   None.

Exceptions

   1)  The cardinality of the input `window' must be even. Left
       endpoints of stored intervals must be strictly greater than
       preceding right endpoints. Right endpoints must be greater
       than or equal to corresponding left endpoints. Invalid window
       data are not diagnosed by this routine and may lead to
       unpredictable results.

   2)  If `smlint' is less than or equal to zero, this routine has
       no effect on the window.

   3)  If the `window' cell argument has a type other than
       SpiceDouble, the error SPICE(TYPEMISMATCH) is signaled.

Files

   None.

Particulars

   This routine removes from the input window every interval with
   measure less than or equal to the limiting measure `smlint'.

Examples

   The numerical results shown for these examples may differ across
   platforms. The results depend on the SPICE kernels used as input,
   the compiler and supporting libraries, and the machine specific
   arithmetic implementation.

   1) Given a double precision window, containing the following four
      intervals:

         [ 1.0, 3.0 ], [ 7.0, 11.0 ], [ 23.0, 27.0 ], [ 29.0, 29.0 ]

      remove any intervals equal to or less than 3.0.


      Example code begins here.


      /.
         Program wnfltd_ex1
      ./
      #include <stdio.h>
      #include "SpiceUsr.h"

      int main()
      {

         /.
         Local parameters.
         ./
         #define WNSIZE           10

         /.
         Local variables.
         ./
         SpiceDouble              left;
         SpiceDouble              right;

         SPICEDOUBLE_CELL ( window,  WNSIZE );

         SpiceInt                 i;

         /.
         Validate the window with size WNSIZE and zero elements.
         ./
         wnvald_c ( WNSIZE, 0, &window );

         /.
         Insert the intervals

            [ 1, 3 ]  [ 7, 11 ]  [ 23, 27 ]  [ 29, 29 ]

         into `window'.
         ./
         wninsd_c (  1.0,   3.0, &window );
         wninsd_c (  7.0,  11.0, &window );
         wninsd_c ( 23.0,  27.0, &window );
         wninsd_c ( 29.0,  29.0, &window );

         /.
         Loop over the number of intervals in `window', output
         the `left' and `right' endpoints for each interval.
         ./
         printf( "Initial window:\n" );
         for ( i=0; i<wncard_c(&window); i++)
         {
            wnfetd_c( &window, i, &left, &right );
            printf("   Interval %d [%8.3f, %8.3f]\n", i, left, right );
         }

         /.
         Filter the intervals smaller than or equal to 3.0
         ./
         wnfltd_c ( 3.0, &window );

         /.
         Output the intervals.
         ./
         printf( "\nWindow after filtering intervals <= 3.0:\n" );
         for ( i=0; i<wncard_c(&window); i++)
         {
            wnfetd_c( &window, i, &left, &right );
            printf("   Interval %d [%8.3f, %8.3f]\n", i, left, right );
         }

         return ( 0 );

      }


      When this program was executed on a Mac/Intel/cc/64-bit
      platform, the output was:


      Initial window:
         Interval 0 [   1.000,    3.000]
         Interval 1 [   7.000,   11.000]
         Interval 2 [  23.000,   27.000]
         Interval 3 [  29.000,   29.000]

      Window after filtering intervals <= 3.0:
         Interval 0 [   7.000,   11.000]
         Interval 1 [  23.000,   27.000]


   2) Using the same window from the first example:

         [ 1.0, 3.0 ]  [ 7.0, 11.0 ]  [ 23.0, 27.0 ]  [ 29.0, 29.0 ]

      Then the following series of calls

         wnfltd_c (  0.0, &window );                             (1)
         wnfltd_c (  2.0, &window );                             (2)
         wnfltd_c (  3.0, &window );                             (3)

      produces the following series of windows

         [ 1.0, 3.0 ]   [ 7.0, 11.0 ]  [ 23.0, 27.0 ]            (1)
                        [ 7.0, 11.0 ]  [ 23.0, 27.0 ]            (2)
                        [ 7.0, 11.0 ]  [ 23.0, 27.0 ]            (3)

Restrictions

   None.

Literature_References

   None.

Author_and_Institution

   N.J. Bachman        (JPL)
   J. Diaz del Rio     (ODC Space)
   H.A. Neilan         (JPL)
   W.L. Taber          (JPL)
   I.M. Underwood      (JPL)

Version

   -CSPICE Version 1.1.0, 05-AUG-2021 (JDR)

       Changed input argument name "small" to "smlint" for consistency
       with other routines.

       Edited the header to comply with NAIF standard. Added complete code
       example based on existing example.

       Extended description of argument "window" in -Detailed_Input to include
       type and preferred declaration method.

       Added entry #1 in -Exceptions section.

   -CSPICE Version 1.0.0, 21-JUL-2002 (NJB) (HAN) (WLT) (IMU)

Index_Entries

   filter small intervals from a d.p. window

Link to routine wnfltd_c source file wnfltd_c.c