3.9.2 Choosing which data to plot
The final modifier which the plot command takes to allow the user to specify which subset(s) of a data file should be plotted is select. This can be used to plot only those data points in a data file which satisfy 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 data points (see Section 3.13 for more information about Pyxplot’s plotting styles), the default behaviour is for the lines not to be broken if a set of data points 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 ($2>0) discontinuous
which plots a set of disconnected peaks from the sine function.