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Tutorial:

4. Extracting, saving, and restoring 3-D time-series

This section of the tutorial will explain various methods for extracting 3-D time-series of data from the HDF files, and how to save and restore these data for future analysis. You will learn how to use:

PPP_EXTRACT - Extracting a 3-D slice of data and associated metadata from the HDF files

You can use PPP_EXTRACT to read a 3-D slice of P-Cube or TOVS Path-P data for a given SDS and range of dates. PPP_EXTRACT is a function with two required arguments, a named variable which will be returned with the extracted data, and the sds_name to extract. Like PPP_STATS, PPP_ANIMATE and PPP_PLOT, it accepts the DATES keyword or a range of dates bounded by START_DATE and END_DATE. It also accepts keywords for two additional portions of metadata from the HDF files: LABELS designates a named variable that will be returned with a string array of dates for each layer of the 3-D data, and SDS_INFO designates a named variable that will be returned with a structure containing the SDS metadata.

P-cube Example
TOVS Path-P Example

Please refer to the Extended Help Documentation for details on the other keywords to PPP_EXTRACT.

PPP_SAVE and PPP_RESTORE - Saving and restoring a 3-D slice and metadata to/from an external file

You can use PPP_SAVE and PPP_RESTORE to write/restore the data and metadata from PPP_EXTRACT to/from an external file, for use in other IDL sessions. Both routines have four required arguments, the data array, the SDS_INFO structure, a string array of date labels, (one for each date layer in the data array), and the name of the external file. Using the returned variables from the PPP_EXTRACT call, above, try:

P-cube Example
TOVS Path-P Example


The restored variables will contain copies of the originals. Please refer to the Extended Help Documentation for details on using PPP_SAVE and PPP_RESTORE.

Next tutorial section (for P-cube CD users only)