Controlling Axis Features

To enable you to control axis features within each of the layout types, there are different sets of axis options for the different types of axes:

The options that are available for each layout are documented separately, but it is worth discussing the following tasks in general for all of the layout types:

Within any given layout in the graph display, each plot axis is always of a particular type. In the default cases, the axis type is always LINEAR, DISCRETE, or TIME.

The axis options for each layout statement include a TYPE= option that enables you to specify an axis type that overrides the default selection mechanisms. When you override the default axis type, you must be sure to specify the correct axis type for the plots that you are defining. For every plot in the template language, the documentation indicates what axis types it supports. Plots statements that are specified in the template are ignored if they are incompatible with the axis type.

Each axis type has features specific to that type, and the following axis options enable you to specify features for the different types:

LINEAROPTS = (linear-suboptions)
DISCRETEOPTS = (discrete-suboptions)
TIMEOPTS= (time-suboptions)
LOGOPTS = (log-suboptions)

One or more of these options can be specified for an axis, but the specified settings are applied only to the axis type that supports them.

For example, a bar chart has two axes – a TYPE=DISCRETE axis for the X axis and a TYPE=LINEAR axis for the Y axis. If a numeric column (for example, Age) is assigned to the X role, this column’s values are always treated as discrete values, never as a continuous range of values. You cannot request another axis type for the X axis, but you can request a different axis type for the Y axis.

Sometimes you want a specialized axis type depending on the nature of the data. For example, if the data have a very large range of values (orders of magnitude apart), you could request that the values be displayed on a logarithmic scale. To set a logarithmic scale, use the TYPE=LOG axis option.

Time series data benefit from displaying the X axis with a TYPE=TIME axis. A TIME axis type requires that the column values are SAS Date, Time, or Datetime values.

Three-dimensional plots such as BIHISTOGRAM3DPARM and SURFACEPLOTPARM always use TYPE=LINEAR for X, Y, and Z axes.

The VIEWMIN= and VIEWMAX= axis options can be used to adjust the view of an axis. You can specify minimum data values to include in the display, maximum data values, or both (the specified values might be adjusted by the threshold calculation). By default, the VIEWMIN= value is the minimum data value for the specified axis and the VIEWMAX= value is the maximum data value for the specified axis.

A VIEWMIN= value that is greater than the data minimum or a VIEWMAX= value that is less than the data maximum acts like a “zoom in” operation. The adjusted view reduces the range of values represented on the axis and can sometimes exclude markers, lines, or fills that would normally appear.

A VIEWMIN= value that is less than the data minimum or a VIEWMAX= value that is greater than the data maximum acts like a “zoom out” operation. The adjusted view extends the range of values represented on the axis and sometimes compresses the markers, lines, or fills into a smaller area.

The following figure shows how the view settings can affect the tick and data displays.

On a continuous, linear axis, the THRESHOLDMIN = and THRESHOLDMAX = axis options can be used to set a bias for including one more tick mark outside of either end of the data range (or VIEWMIN to VIEWMAX range). The threshold range is from 0 (do not include the tick mark) to 1 (include the tick mark). The default is 0.30. The bias at the minimum end of the axis is calculated using the THRESHOLDMIN= value and the minimum data value (by default) or the VIEWMIN= value (if set).

The bias at the maximum end of the axis is calculated using the THRESHOLDMAX= value and the maximum data value (by default) or the VIEWMAX= value (if set).

Specifying THRESHOLDMIN=0 and THRESHOLDMAX=0 prevents the tick marks from extending beyond the data range. Specifying THRESHOLDMIN=1 and THRESHOLDMAX=1 ensures that the data range is bounded by tick marks.

The following figure shows how the threshold settings can affect the tick display on an axis. In the figure, 8 is the minimum value for the display and 29 is the maximum value.

The OFFSETMIN = and OFFSETMAX = axis options can be used to reserve an area at the minimum end of an axis, the maximum end, or both ends. No tick marks are displayed in the reserved areas.

The offset range is from 0 to 1, and the specified value is used to calculate the offset as a percentage of the full axis length. The larger the offset area that is reserved, the less space is available for the tick display area. The default offset reserves just enough area to fully display markers and other graphical features near the ends of an axis.

The following figure shows how offset values of 0.08 might compare with the default offsets for a continuous axis.

This next figure shows how offset values might affect the discrete axis of a bar chart.