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vnormg_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

```   vnormg_c ( Vector norm, general dimension )

SpiceDouble vnormg_c ( ConstSpiceDouble   * v1,
SpiceInt             ndim )

```

#### Abstract

```   Compute the magnitude of a double precision vector of arbitrary
dimension.
```

```   None.
```

#### Keywords

```   VECTOR

```

#### Brief_I/O

```   VARIABLE  I/O  DESCRIPTION
--------  ---  --------------------------------------------------
v1         I   Vector whose magnitude is to be found.
ndim       I   Dimension of `v1'.

The function returns the magnitude of `v1'.
```

#### Detailed_Input

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

ndim        is the dimension of the input vector `v1'.
```

#### Detailed_Output

```   The function returns the magnitude of `v1' calculated in a
numerically stable way.
```

#### Parameters

```   None.
```

#### Exceptions

```   Error free.
```

#### Files

```   None.
```

#### Particulars

```   vnormg_c finds the component of v1 whose magnitude is the largest.
If the absolute magnitude of that component indicates that a
numeric overflow would occur when it is squared, or if it
indicates that an underflow would occur when squared (falsely
giving a magnitude of zero) then the following expression is
used:

vnormg_c = v1max * MAGNITUDE OF [ (1/v1max)*v1 ]

Otherwise a simpler expression is used:

vnormg_c = MAGNITUDE OF [ v1 ]

Beyond the logic described above, no further checking of the
validity of the input is performed.
```

#### Examples

```   The numerical results shown for these examples 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 four-dimensional vector and calculate its magnitude.

Example code begins here.

/.
Program vnormg_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"

int main( )
{

/.
Local parameters.
./
#define NDIM         4

/.
Local variables.
./
SpiceDouble          v1    [NDIM] = { 12.3, -4.32, 76.0, 1.87 };

/.
Compute the magnitude of `v1'
./
printf(" Magnitude of v1: %f\n", vnormg_c( v1, NDIM ) );

return ( 0 );
}

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

Magnitude of v1: 77.132673

2) The following table show the correlation between various input
vectors `v1' and vnormg_c:

ndim     v1[ndim]                          vnormg_c
---------------------------------------------------
1      (-7.0e20)                            7.e20
3      (1., 2., 2.)                         3.
4      (3., 3., 3., 3.)                     6.
5      (5., 12., 0., 0., 0.)               13.
3      (-5.e-17, 0.0, 12.e-17)             13.e-17
```

#### Restrictions

```   None.
```

#### Literature_References

```   None.
```

#### Author_and_Institution

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

#### Version

```   -CSPICE Version 1.2.0, 13-AUG-2021 (JDR)

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

Removed check for "ndim" being positive in order to replicate
behavior of SPICELIB equivalent routine.

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

Made input vector const.

-CSPICE Version 1.0.0, 01-APR-1998 (EDW) (WMO)
```

#### Index_Entries

```   norm of n-dimensional vector
```
`Fri Dec 31 18:41:15 2021`