CSPICE Routines: TRACE

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TRACE_C: Trace of a 3x3 matrix

Abstract
```
    Return the trace of a 3x3 matrix. 
```
Required_Reading
```
   None. 
```

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. 
```

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.

Exceptions
```
    Error free. 
```
Files
```
    None 
```

Author_and_Institution

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

Literature_References
```
    None 
```
Version
```
   -CSPICE Version 1.0.0, 29-JUN-1999
```
Index_Entries
```
   trace of a 3x3_matrix 
```
Link to routine source

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