major-tic-increment

Arguments: value-axis

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

The value increment between successive major tic positions of a value-axis in a chart-widget. The value should be a positive real number, or else nil for the value to be computed automatically. The default value is nil.

When the value is computed automatically, this is done after the range-bottom and range-top of the value-axis have been determined. Then a major-tic-increment is chosen such that there are a few major increments between the range-bottom and range-top, at relatively "round" values.

As an example of specifying this property explicitly, let's say that you have data values that range from 307 to 384. If you set the range-bottom property to 300 and range-top to 400, then setting major-tic-increment to 20 would produce major tic positions at 300, 320, 340, 360, 380, and 400. Setting minor-tics-per-major-tic to 4 would then produce minor tic positions at 300, 305, 310, 315, 320, and so on.

To make the values increase in the atypical direction, use invert-axis rather than a negative major-tic-increment.

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

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Created 2010.1.21.