Procedure

   SpiceDouble trace_c ( ConstSpiceDouble  matrix[3][3] ) 

Abstract

 
    Return the trace of a 3x3 matrix. 
 

Required_Reading

 
   None. 
 

Keywords

 
    MATRIX 
 

Brief_I/O

 
    VARIABLE  I/O  DESCRIPTION 
    --------  ---  -------------------------------------------------- 
    matrix     I     3x3 matrix of double precision numbers. 
    trace      O     The trace of matrix. 
 

Detailed_Input

 
    matrix  is a double precision 3x3 matrix. 
 

Detailed_Output

 
    trace   is the trace of matrix, i.e. it is the sum of the 
            diagonal elements of matrix. 
 

Parameters

 
   None. 
 

Exceptions

 
    Error free. 
 

Files

 
    None 
 

Particulars

 
    trace_c simply executes in C code the following loop: 
 
    trace_c = Summation from i = 1 to 3 of matrix[i][i]
 
    This functions implements no error detection. 
 

Examples

 
                          | 3   5   7 | 
    Suppose that matrix = | 0  -2   8 |  , then 
                          | 4   0  -1 | 
 
    trace_c (matrix) = 0.  (which is the sum of 3, -2 and -1). 
 

Restrictions

 
    No checking is performed to guard against floating point overflow 
    or underflow.  This routine should probably not be used if the 
    input matrix is expected to have large double precision numbers 
    along the diagonal. 
 

Literature_References

 
    None 
 

Author_and_Institution

 
    W.L. Taber      (JPL) 
    E.D. Wright     (JPL)
 

Version

 
   -CSPICE Version 1.0.0, 29-JUN-1999

Index_Entries

 
   trace of a 3x3_matrix 
 

Link to routine trace_c source file trace_c.c