Axis Titles and Tickmark Text

You can supply an axis title for an axis by setting the TITLE property equal to the object reference of an IDLgrText object. Text objects connected to axis objects via the TITLE property are automatically centered under or next to the axis they belong with.

Note
Titles and tickmark text inherit the color specified for the IDLgrAxis object itself, even if the COLOR property is specified for the IDLgrText object specified, unless the USE_TEXT_COLOR property for the axis is nonzero.

By default, major tick marks are labelled with the data values. You can supply a set of tickmark text values by setting the TICKTEXT property equal to either a single instance of an IDLgrText object containing a vector of text strings or to a vector of IDLgrText objects, each of which contains a single text string.

Note
Make sure that you have the same number of tick label strings as there are major tick marks for the axis.

Reverse Axis Plotting

IDL also allows you to plot data in Object Graphics by reversing the order of axis tick values. This is known as reverse axis plotting.

When using Object Graphics, each core object is a building block. Any number of building blocks may be combined together in a hierarchical tree to create an overall scene. An individual object is not aware of the other objects in the hierarchy; therefore, the designer of the hierarchy must control all interactions between the objects. For example, to properly display a reverse axis plot in Object Graphics, the designer must appropriately set the properties on the X axis, the Y axis, and the plot line, each of which contribute to the overall displayed results.

Example Code
You can run this example by entering EX_REVERSE_PLOT at the IDL command line. You can view the source for this example, ex_reverse_plot.pro, in the examples/doc/objects directory. Run the example procedure by entering ex_reverse_plot at the IDL command prompt or view the file in an IDL Editor window by entering .EDIT ex_reverse_plot.pro.

The following figure demonstrates how you can reverse the order of axis tick values using Object Graphics.