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Дата изменения: Fri Jan 10 22:39:39 2003
Дата индексирования: Sat Dec 22 07:43:12 2007
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XMM-Newton Science Analysis System


implot (implot-2.5.2) [xmmsas_20030110_1802-5.4.1]

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Maximum number of sources.

It may be desirable to apply (in addition to the source selection described above) some definite upper limit to the number of sources to be plotted - say, to plot only the first 50 brightest sources. Such a limit may be difficult or impossible to achieve by use of the expression parameter. For this reason, an ncut parameter has been provided. However, this parameter alone cannot provide full versatility. It is not sufficient just to specify the number of sources to keep: it is also necessary to determine which sources to keep. This means that the sources must be sorted into a series before the series can be truncated after the ncutth member. Parameters ncutsortstyle and ncutsortexpression have been provided to allow the sources to be sorted.

Parameter ncutsortstyle has the following allowed values:

• radiusup: sources are ordered in order of increasing radius (see subsection 3.5).
• radiusdown: sources are ordered in order of decreasing radius (see subsection 3.5).
• rownumber: sources are ordered in order of increasing row number in the source table.
• expr: for this value, the task looks in parameter ncutsortexpression for an expression involving column names. This expression is evaluated and the sources are then ordered in increasing order of the resulting value.
• none: no truncation: all sources are plotted. This is the default.

NOTE however that the infrastructure to allow the evaluation of arithmetic expressions involving column values is not yet in place (although it is expected to be very soon). At present the only acceptable format for ncutsortexpression (and for parameters radiusexpression and labelsexpression, see subsections 3.5 and 3.6) is a single column name.