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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.



next up previous
Next: Axis Normalisation Flags
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Starlink User Note 33
R.F. Warren-Smith
11th January 2000
E-mail:rfws@star.rl.ac.uk

Copyright © 2000 Council for the Central Laboratory of the Research Councils