8.1 The with modifier
In Chapter 3 an overview of the syntax of the plot command was provided, including the every, index, select and using modifiers, which can be used to control which data should be plotted. The with modifier controls how data should be plotted. For example, the statement
plot "data.dat" index 1 using 4:5 with lines
specifies that data should be plotted with lines connecting each data point to its neighbors. We term the keyword lines a plot style. The with modifier can also be followed by a variety of settings which fine-tune aspects of how data are displayed. For example, the statement
plot "data.dat" with lines linewidth 2.0
would connect data points with a line of twice the default width.
The next section will provide a complete list of all of Pyxplot’s plot styles – i.e. the words which may be used in place of lines. First we list all of the modifiers such as linewidth which may be used to alter the exact appearance of these plot styles. These are as follows:
Any number of these modifiers may be placed sequentially after the keyword with, as in the following examples:
plot 'datafile' using 1:2 with points pointsize 2 plot 'datafile' using 1:2 with lines color red linewidth 2 plot 'datafile' using 1:2 with lp col 1 lw 2 ps 3
Where modifiers take numerical values, expressions of the form $2+1, similar to those supplied to the using modifier, may be used to read numbers from the supplied data set. In this case, each datapoint will be displayed in a different style or in a different color (in the example given, depending on the values in the second column of the supplied data).
The following example would plot a data file with points, drawing the position of each point from the first two columns of the supplied data file and the size of each point from the third column:
plot 'datafile' using 1:2 with points pointsize $3
Not all of these modifiers are applicable to all of Pyxplot’s plot styles. For example, the linewidth modifier has no effect on plot styles which do not draw lines between datapoints. Where modifiers are applied to plot styles for which they have no defined effect, the modifier has no effect, but no error results. Table 8.1 lists which modifiers act on which plot styles.