You may also change the type of the line that is drawn by changing the value of the system variable !P.LINESTYLE, or by using the keyword LINESTYLE for individual plots. The default value is 0, a solid line. To get dotted lines, set !P.LINESTYLE equal to 1. Other options are listed in the IDL User's Guide.
OPLOT WARNING: Users with GraphOn terminals (such as those in the IUEDAC terminal room) who are overplotting with the LINESTYLE keyword or the !P.LINESTYLE system variable set to a positive value should execute the OPLOT command in the graphics window. If the OPLOT command is given from the alphanumerics window, the data will be overplotted using a solid line. For the case where LINESTYLE=2, your terminal will be reset, and both windows will be cleared! If you wish, you may type the OPLOT command in the alpha window, but be sure to hit the STATUS/WINDOW key to switch to the graphics window before hitting return.