The final modifier which the plot command takes to allow the user to specify which subset(s) of a datafile should be plotted is select. This can be used to plot only those datapoints in a datafile which specify some given criterion, as in the following examples:
plot 'data.dat' select ($8>5) plot sin(x) select (($1>0) and ($2>0))
In the second example, two selection criteria are given, combined with the logical and operator. A full list of all of the operators recognised by PyXPlot, including logical operators, was given in Table 3.1.
When plotting using lines to connect the datapoints (see Section 3.13), the default behaviour is for the lines not to be broken if a set of datapoints are removed by the select modifier. However, this behaviour is sometimes undesirable. To cause the plotted line to break when points are removed the discontinuous modifier is supplied after the select modifier, as in the example
plot sin(x) select ($1>0) discontinuous
which plots a set of disconnected peaks from the sine function.