/*****************************************************************************
*                                                                            *
*   TRACE.SPL    Copyright (C) 2001 DSP Development Corporation              *
*                               All Rights Reserved                          *
*                                                                            *
*   Author:      Randy Race                                                  *
*                                                                            *
*   Synopsis:    Trace of an array                                           *
*                                                                            *
*   Revisions:    9 Aug 2001  RRR  Creation                                  *
*                                                                            *
*****************************************************************************/

#include 

#if @HELP_TRACE

    TRACE

    Purpose: Calculates the trace of an array, the sum of the diagonal elements

    Syntax:  TRACE(a)

                  a - input array, defaults to the current series


    Returns: A real, the diagonal sum.

    Example:
             W1: {{1, 2, 3},
                  {4, 5, 6},
                  {7, 8, 9}}

             trace(w1) == 15

    Remarks:
             TRACE defaults to the current series if no input is
             supplied.

    See Also:
             Diag
             Sum
#endif


/* trace of an array */
trace(a)
{
        local w, rank, nc, nr;

        if (argc < 1)
        {
                a = refseries(1);
        }

        /* cast non-arrays to an array */
        if (not(isarray(a))) a = {a};

        return(sum(diag(a)));
}