ISeries.FirstValueIndex
ISeries

property FirstValueIndex: Integer;

Type Library
TeeChartx

Description
This function / property returns the ValueIndex of the First point in the Series that has an X value which is between the Horizontal Axis Maximum and Minimum values.

When no Zoom is applied to the Chart, and the Axis are Automatic, the FirstValueIndex is 0. If the Series has no points or there are no visible points, the FirstValueIndex returns -1.