The plot points as shown in Figure 2 can be put at any location on the plot window as markers. This is done with the oplot_marker() command
Ifeffit> plot_marker(x=7000,y=4,marker=1) Ifeffit> plot_marker(7000,2,3)where the value of marker gives the integer from Figure 2 for the symbol to use. Like the plot_text() command, this command can use default positional keywords for x, y, and marker, greatly simplifying the syntax.
Arrows and lines can be put anywhere on the plot window, pointing to some spectral feature of the plotted data. This is done with the plot_arrow() command, which takes beginning and end points, and parameters describing how draw the arrow head (including whether to have no arrow head at all). An arrow can be placed like this:
Ifeffit> plot_arrow(x1=7000,y1=4, x2=7050,y2=3)More complex control over the shape of the arrowhead can be obtained with the keywords size, angle, and barb. The size keyword alters the size of the arrowhead, while angle gives the angle subtended by the point in degrees. The barb keyword controls the shape and concavity of the arrowhead. Examples, with reasonable values for the size and barb parameters include
Ifeffit> plot_arrow(x1=10, y1= 4, x2=25, y2=4, barb=2) Ifeffit> plot_arrow(x1=65, y1= 4, x2=90, y2=4, barb=0,outline=1) Ifeffit> plot_arrow(x1=65, y1= 0, x2=90, y2=0, angle=100,barb=0) Ifeffit> plot_arrow(x1=65, y1=-4, x2=90, y2=-4, size=5) Ifeffit> plot_arrow(x1=30, y1= 8, x2=90, y2=8, no_head=1)The result of these and other plot_arrow() commands are shown in Figure 4. The arrowhead can be made hollow by setting outline=1. To get a line between points (x1,y1) and (x2,y2), the plot_arrow() command is used with no_head=1, which completely suppresses the arrowhead.