Accessing Axis Variance Values as Standard Deviations

The values of an axis variance array may also be accessed directly as standard deviation values by specifying the special component name `Error' in a call to NDF_AMAP. This facility operates in exactly the same way as the equivalent operation on the main variance component of an NDF (see §) and causes the square root of the mapped values to be taken before they are returned. If a mapping mode of `UPDATE' or `WRITE' is specified, then the new or modified values are also squared before being written back to the axis array when it is unmapped.

Note that the component name `Error' may only be used with mapping routines. The name `Variance' should be used when later unmapping values accessed in this way.