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XMM-Newton Science Analysis System


evselect (evselect-3.47.8) [xmmsas_20030110_1802-5.4.1]

Meta Index / Home Page / Description / Extraction Stage (extractor)

Event List Output

In addition to the above product files, the result of the filtering stage can be propagated into the output as well. This can be done in four different ways controlled by the two tasks parameters destruct and withfilteredset. The first is a boolean switch selecting either a destructive or non-destructive filtering mode. In the former case, non-selected events shall be physically removed, and, thus will not be present in the final filtered event list. In non-destructive mode, these events are merely flagged by setting a corresponding bit in an integer table column. The name of this column and the bit position to be manipulated can be controlled via the parameters flagcolumn and flagbit. If non-destructive filtering is selected and the named flag-column does not exist, it will be created. The withfilteredset parameter determines whether the input event list is modified according to the above two schemes (withfilteredset=false) or a new event list file is created accordingly. The following table provides a quick overview over the four possible cases:

	destruct=yes	destruct=no
withfilteredset=false	the input file is modified; non-selected events will be removed	the input file is modified by adding an integer flag column indicating each event's selection status
withfilteredset=true	input file is not modified; selected events will be copied to new output file	input file is not modified; all events (selected and non-selected) get copied to new event list file with an integer flag column

If withfilteredset is set to true, then the name of output table file is set with the parameter filteredset. If withfilteredset is set to false, then the parameter keepfilteroutput, which is set to false by default, will prevent one from modifying the input table. If one wishes to modify the input file (either destructively or by flagging) one needs to set keepfilteroutput to true. Note that when evselect produces an output table file, it does so by first creating an exact copy of the input table file, and then preforming all filtering operations on the copy. Thus any extensions in the input file will also appear in the output file.