James TappinInternally, IDL_HS 4 represents a major rewrite of the whole codebase. However, to the user, this should not be a concern.
From the point of view of a user (as opposed to a developer or an installer), the main difference of philosophy is that instead of thinking in terms of programs (e.g. PLOT_RATES or PLOT_PAD) the central concept is that of a dataset.
A dataset is a collection of data and settings that will go to generate an output plot. Five types of dataset are defined; RATES, SPECT, PAD, PHA MATRIX and XFLARE (activity plot) datasets.
It is possible to have several datasets defined simultaneously, and to switch between them, this is unlike V3 where making new settings destroyed the old ones. Most operations are performed on the current dataset.
The data in a dataset are divided into streams; which can be added, deleted and moved within the dataset.
Within a dataset, the data are organized into streams. A stream corresponds to a single channel in RATES or PAD datasets, or a head in a SPECT dataset. (In PAD and SPECT datasets, the internals of the dataset group the streams into the panels that are displayed).
It is possible for different classes of stream to be included in the same dataset; for example a RATES dataset can contain a mixture of HISCALE and EPAM streams, or particle fluxes and magnetic field.
Unlike Version 3, where there was a single data directory; in version 4 there is a search path associated with each class of data. This search path is stored along with the IDF information for the data class. If your installation has been properly set up, then the normal sources of data should be in the search paths when you start the system, if they aren't then complain to whoever installed it.
The IDF information is global (i.e. it applies to all datasets and their streams) but changing an IDF file will not update the information for streams that have already been defined.
The plot setup is very similar to that used in version 3, and is also global. The main changes are that there are now separate spool commands for PS and EPS files.
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The translation was initiated by James Tappin on 2000-08-29