ProEssentials v7 Help .Net Reference

# Common Question 15

## My graph draws lines across Null Data values, how do I tell the graph to form gaps on Null Data values?

There's a property called NullDataGaps which when set to TRUE causes gaps to be formed upon Null Data.

Related to this topic is another property LineGapThreshold. It causes the formation of gaps but does not use Null Data values but rather the distance between any adjacent non-null data points. For the Scientific Graph Object, this distance is the difference between consecutive non-null XData values. For the Graph Object, this distance is the point number difference between consecutive non-null YData values.

For example, a Scientific Graph Object has...

 Pesgo1.LineGapThreshold = 25 ... Pesgo1.XData(0, 10) = 20 Pesgo1.XData(0, 11) = 50

Because 50-20 > 25, this will cause a gap to form in the line between the point indices 10 and 11.

For another example, a Graph Object has ...

 Pego1.LineGapThreshold = 2 Pego1.NullDataValue = -999 ... Pego1.YData(0,10) = 20 Pego1.YData(0,11) = -999 Pego1.YData(0,12) = -999 Pego1.YData(0,13) = 22

Because 13 - 10 > 2, this will cause a gap to form in the line between the point indices 10 and 13. If YData(0,12) had a valid value, a gap would not have been formed and a bridge would have been drawn from point index 10 to 12.

So to summarize, ProEssentials can form gaps or bridges across null data values. It also has a mechanism to form gaps anytime data spans a certain XData range or is missing (null) for a designated number of data points.

Note that anytime two gapped sections surround a single valid data point, that isolated data point will be plotted with a point even though the plotting method is currently a line.

Within the demo and example projects, see example 006.