Anotating the Viewport

The routine plbox is used to specify whether a frame is drawn around the viewport and to control the positions of the axis subdivisions and numeric labels. For our simple graph of the transistor characteristics, we may wish to draw a frame consisting of lines on all four sides of the viewport, and to place numeric labels along the bottom and left hand side. We can also tell PLPLOT to choose a suitable tick interval and the number of subticks between the major divisions based upon the data range specified to plwind. This is done using the following statement

plbox("BCNST",0.0,0,"BCNSTV",0.0,0);

Another routine pllab provides for text labels for the bottom, left hand side and top of the viewport. These labels are not clipped, even though they lie outside the viewport (but they are clipped at the subpage boundaries). pllab actually calls the more general routine plmtex which can be used for plotting labels at any point relative to the viewport. For our example, we may use

pllab("V\\dCE\\u (Volts)","I\\dC\\u (mA)","TRANSISTOR CHARACTERISTICS");

Note that \\d and \\u are escape sequences (see page $[*]$ ) which allow subscripts and superscripts to be used in text. They are described more fully later in this chapter.

The heights of characters used for the axis and graph labels can be changed by means of the routine plschr.