Labelling the graph

The function pllab may be called after plenv to write labels on the x and y axes, and at the top of the picture. All the variables are character variables or constants. Trailing spaces are removed and the label is centred in the appropriate field. The syntax for pllab is:

pllab(xlbl,ylbl,toplbl); xlbl (char *, input) Pointer to string with label for the X-axis (bottom of graph). ylbl (char *, input) Pointer to string with label for the Y-axis (left of graph). toplbl (char *, input) Pointer to string with label for the plot (top of picture).

More complex labels can be drawn using the function rouplmtex. See also Section $[*]$ on page $[*]$ for information about the function plptex which writes labels within a graph.