plot-values-max-index

Arguments: plot-widget

Returns the value of the plot-values-max-index property of a plot-widget. The value may be set at creation time by passing a plot-values-max-index initarg to make-instance, or any time later by calling (setf plot-values-max-index).

plot-values-max-index is the index of the last plot value of a plot-widget that should be displayed at the current time. The value should be a non-negative integer, or else nil for no maximum. The default value is nil.

If set-plot-value has been used to add values to the plot, then any value whose index is greater than this property value (if it is a number) will not appear in the plot. When the property value is nil, then no items are excluded. This property can be used to display a subset of collected values that are of interest at the moment.

If instead a plot-value-returner function is used for looking up plot data, then this property should always be set to a non-negative integer to tell the plot the maximum value index that it should pass to the plot-value-returner function. Otherwise the plot-widget has no way of knowing how many values your function is prepared to return. (The property will arbitrarily default to 100 in this case, though that would usually not match your available data.)

This property is the maximum index that will be included, rather than the number of indexes to include. So for a plot-value-returner function to cover all values from a 100-element vector, for example, the value of this property should be 99 rather than 100.

If a plot-value-returner function is used, and some chart objects have more data points than others, then this property should be set to the high enough to cover the object that has the most points. And the plot-value-returner function should return nil (rather than breaking) if it is passed an index for some other object that is beyond the number of data points for that object.

See also plot-values-min-index.

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