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unormg_c

 Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input Detailed_Output Parameters Exceptions Files Particulars Examples Restrictions Literature_References Author_and_Institution Version Index_Entries

#### Procedure

```   unormg_c ( Unit vector and norm, general dimension )

void unormg_c ( ConstSpiceDouble    v1     [],
SpiceInt            ndim,
SpiceDouble         vout   [],
SpiceDouble       * vmag    )

```

#### Abstract

```   Normalize a double precision vector of arbitrary dimension and
return its magnitude.
```

```   None.
```

#### Keywords

```   VECTOR

```

#### Brief_I/O

```   VARIABLE  I/O  DESCRIPTION
--------  ---  --------------------------------------------------
v1         I   Vector to be normalized.
ndim       I   Dimension of `v1' (and also `vout').
vout       O   Unit vector v1 / ||v1||.
vmag       O   Magnitude of `v1', i.e. ||v1||.
```

#### Detailed_Input

```   v1          is an arbitrary double precision n-dimensional vector,
including the zero vector.

ndim        is the dimension of `v1' and `vout'.
```

#### Detailed_Output

```   vout        is the double precision n-dimensional unit vector in the
direction of `v1'. If `v1' is the zero vector, then `vout'
will also be the zero vector.

vmag        is the magnitude of `v1'.
```

#### Parameters

```   None.
```

#### Exceptions

```   Error free.
```

#### Files

```   None.
```

#### Particulars

```   unormg_c references a function called vnormg_c (which itself is
numerically stable) to calculate the norm of the input vector `v1'.
If the norm is equal to zero, then each component of the output
vector `vout' is set to zero. Otherwise, `vout' is calculated by
dividing `v1' by the norm. No error detection or correction is
implemented.
```

#### Examples

```   The numerical results shown for this example 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) Define a set of n-dimensional vectors and compute their
corresponding unit vectors and magnitudes.

Example code begins here.

/.
Program unormg_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"

int main( )
{

/.
Local parameters.
./
#define NDIM         4
#define SETSIZ       2

/.
Local variables.
./
SpiceDouble          vmag;
SpiceDouble          vout   [NDIM];

SpiceInt             i;

/.
Define the vector set.
./
SpiceDouble          v1     [SETSIZ][NDIM] = {
{ 5.0,   12.0,   0.0,   4.0 },
{ 1.e-6,  2.e-6, 2.e-6, 0.0 } };

/.
Calculate the unit vectors and magnitudes.
./
for ( i = 0; i < SETSIZ; i++ )
{
unormg_c ( v1[i], NDIM, vout, &vmag );

printf( "Vector     : %11.7f %11.7f %11.7f %11.7f\n",
v1[i][0], v1[i][1], v1[i][2], v1[i][3] );
printf( "Unit vector: %11.7f %11.7f %11.7f %11.7f\n",
vout[0], vout[1], vout[2], vout[3] );
printf( "Magnitude  : %11.7f\n", vmag );
printf( "\n" );
}

return ( 0 );
}

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

Vector     :   5.0000000  12.0000000   0.0000000   4.0000000
Unit vector:   0.3676073   0.8822575   0.0000000   0.2940858
Magnitude  :  13.6014705

Vector     :   0.0000010   0.0000020   0.0000020   0.0000000
Unit vector:   0.3333333   0.6666667   0.6666667   0.0000000
Magnitude  :   0.0000030
```

#### Restrictions

```   1)  No error checking is implemented in this function to guard
against numeric overflow.
```

#### Literature_References

```   None.
```

#### Author_and_Institution

```   N.J. Bachman        (JPL)
J. Diaz del Rio     (ODC Space)
E.D. Wright         (JPL)
```

#### Version

```   -CSPICE Version 1.3.0, 05-JUL-2021 (JDR)

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

Updated wrapper to call f2c'ed SPICELIB version.

-CSPICE Version 1.2.0, 06-FEB-2017 (EDW)

Bug fix: eliminated spurious semi-colon on "for(...)" line.
This caused the output vector not to be set when the input
argument `v1' was the zero vector.

Corrected section order.

-CSPICE Version 1.1.0, 22-OCT-1998 (NJB)

Made input vector const. Converted check-in style to discovery.

-CSPICE Version 1.0.0, 31-MAR-1998 (EDW)
```

#### Index_Entries

```   n-dimensional unit vector and norm
```
`Fri Dec 31 18:41:14 2021`