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vhatg_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

```   vhatg_c ( "V-Hat", unit vector along V, general dimension )

void vhatg_c ( ConstSpiceDouble   * v1,
SpiceInt             ndim,
SpiceDouble        * vout )

```

#### Abstract

```   Find the unit vector along a double precision vector of
arbitrary dimension.
```

```   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 along `v1'.
```

#### Detailed_Input

```   v1          is any double precision vector of arbitrary dimension.

ndim        is the dimension of `v1' (and also `vout').
```

#### Detailed_Output

```   vout        is the unit vector in the direction of `v1':

v1
vout = --------
||v1||

If `v1' represents the zero vector, then `vout' will also be
the zero vector. `vout' may overwrite `v1'.
```

#### Parameters

```   None.
```

#### Exceptions

```   Error free.
```

#### Files

```   None.
```

#### Particulars

```   vhatg_c determines the magnitude of `v1' and then divides each
component of `v1' by the magnitude. This process is highly stable
over the whole range of multi-dimensional vectors.

This routine will detect if `v1' the zero vector, and will not
attempt to divide by zero.
```

#### 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 find the unit vector
along each of them.

Example code begins here.

/.
Program vhatg_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"

int main( )
{

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

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

SpiceInt             i;

/.
Define the vector set.
./
SpiceDouble          v1     [SETSIZ][NDIM] = {
{ 5.0,    12.0,  0.0,   0.0 },
{ 1.e-7,  2.e-7, 2.e-7, 0.0 } };

/.
Calculate the unit vectors.
./
for ( i = 0; i < SETSIZ; i++ )
{

vhatg_c ( v1[i], NDIM, vout );

printf( "Input 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( "\n" );

}

return ( 0 );
}

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

Input vector:    5.0000000  12.0000000   0.0000000   0.0000000
Unit vector :    0.3846154   0.9230769   0.0000000   0.0000000

Input vector:    0.0000001   0.0000002   0.0000002   0.0000000
Unit vector :    0.3333333   0.6666667   0.6666667   0.0000000
```

#### Restrictions

```   1)  The relative number of cases whereby floating point overflow
may occur is negligible. Thus, no error recovery or reporting
scheme is incorporated into this function.
```

#### Literature_References

```   None.
```

#### Author_and_Institution

```   N.J. Bachman        (JPL)
J. Diaz del Rio     (ODC Space)
W.M. Owen           (JPL)
```

#### Version

```   -CSPICE Version 1.0.1, 05-JUL-2021 (JDR)

```   unitize a n-dimensional vector
`Fri Dec 31 18:41:14 2021`