SubsetByPoint

Purpose

This property controls how two dimensional property arrays (example, YData, XData) are stored internally. Two dimensional arrays are really stored as a series of bytes. This property controls how that series of bytes is structured.

Comments

This property is only of consequence under two situations: 1) When you do not know either the number of subsets or points being graphed and want to incrementally add/subtract data to the graph in one pass (example, gathering data from an SQL statement), and 2) You need to adjust the number of subsets or points being graphed and also need to preserve the existing data already in the control.

This property facilitates the structuring of data so that additions and subtractions in data can be accomplished without mangling the existing data format and also allows optimizing performance in adding or subtracting data.

If this property is TRUE, 2d data is stored subset by point.

Subset by Point Data Format   

This form allows for quick additions and subtractions of a subset(s) worth of data. In other words, adding/subtracting all points for a particular subset(s).

For example, your user can run from 1 to 10 equipment tests (1-10 subset) each consisting of 500 samples (500 points). You need to add test run results (increasing Subsets) without effecting the format of existing data.

When using the WinForm, OCX or VCL interfaces, or when using the PEvsetcellEx and PEvgetcellEx functions, the one dimensional offset is automatically calculated from the given subset and point indices. However, when using PEvsetcell or PEvgetcell, with two dimensional property arrays (like YData) calculating the zero based single dimensional index is as follows:

offset = (TargetSubset X Points) + TargetPoint

If this property is FALSE, 2d data is stored point by subset.

Point by Subset Data Format   

This form allows for quick additions and subtractions of a point(s) worth of data. In other words, adding/subtracting all subsets for a particular point(s).

For example, you are executing an SQL statement gathering 5 fields of data (5 subsets) but you do not know how many records are contained in the database until after the SQL executes. In this form, you can efficiently increase the Points property with each new record read.

When using the WinForm, OCX or VCL interfaces, or when using the PEvsetcellEx and PEvgetcellEx functions, the one dimensional offset is automatically calculated from the given subset and point indices. However, when using PEvsetcell or PEvgetcell with two dimensional property arrays (like YData) calculating the zero based single dimensional index is as follows:

offset = (TargetPoint X Subsets) + TargetSubset