do.first allows the user to execute one or more commands before displaying values on a plot.
do.first is an argument in some plotrix functions that allows the user to do things like add a background color or a grid to the plot before displaying the other plot elements.
The value of do.first should be a character string that can be parsed to one or more valid R commands. Remember to enclose the string in quotes, separate commands with semicolons and escape quotes within the string with backslashes if necessary.