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 withncut, ncutsortstyle and ncutsortexpression have been provided to allow the sources to be sorted.
Parameter ncutsortstyle has the following allowed values:
