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Creating a Delta Array

To create a DELTA array, first store the uncompressed integer values in a simple array, and then copy the array using ARY_DELTA. The copy produced by ARY_DELTA will be stored in DELTA form.

Arrays of floating point values may be compressed by first storing the floating point values in a SCALED array, and then using ARY_DELTA to create a delta compressed copy of the scaled array. Note, the scaled array must use an integer data type to store the internal (i.e. scaled) values. The use of the scaled array means that the compression is not lossless, since some information will have been lost in scaling the floating point values into integers.



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Next: The HDS Structure of a Delta Array
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ARY [2.5ex
Starlink User Note 11
R.F. Warren-Smith & D.S. Berry
19th July 2012
E-mail:starlink@jiscmail.ac.uk

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