range-bottom

Arguments: value-axis

Returns the value of the range-bottom property of a value-axis. The value may be set at creation time by passing the range-bottom initarg, or any time later by calling (setf range-bottom).

A value to use for the low end of a value-axis in a chart-widget. The value should be a real number, or else nil to have the value computed automatically. The default value is nil.

When the value is a number, it should typically be less than or equal to the smallest data value that is being charted, or at least lower than the smallest value that you are interested in viewing at the moment.

When the value is computed automatically, a relatively "round" number is chosen that is equal to or somewhat less than the smallest data value. If set-chart-value is later called to add a value that is less than the current automatically computed range bottom, then a new range bottom will be computed to encompass the new value.

The value should be less than the range-top. To make the values increase in the atypical direction, use invert-axis rather than a range-bottom that is greater than the range-top.

To force a new range bottom to be computed (when the value of this property is nil), call update-chart-widget. This may be useful to recompute the range after set-chart-value has been used to modify values so that the data range is smaller, or if something has changed to cause the widget's chart-value-returner function to return a different range of values.

See also major-tic-increment and minor-tics-per-major-tic.

See chart-widget and also cg-chart-widget.htm.

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This page was not revised from the 8.1 page.
Created 2010.1.21.