Low-level plotting commands

Sometimes the high-level plotting functions don't produce exactly the kind of plot you desire. In this case, low-level plotting commands can be used to add extra information (such as points, lines or text) to the current plot.

Some of the more useful low-level plotting functions are:

$\begin{session} \separate points(x,y) lines(x,y) & Adds points or connected line... ... calling {\tt plot()} with the {\tt axes=F} argument.\cr \separate \end{session}$

Low-level plotting functions usually require some positioning information (e.g. x and y coordinates) to determine where to place the new plot elements. Coordinates are given in terms of user coordinates which are defined by the previous high-level graphics command and are chosen based on the supplied data.

Where x and y arguments are required, it is also sufficient to supply a single argument being a list with elements named x and y. Similarly a matrix with two columns is also valid input. In this way functions such as locator() (see below) may be used to specify positions on a plot interactively.

Jeff Banfield
2/13/1998