Line chart is slow for large regression problems

[bburlacu]

When the problem data contains a large number of rows (20000-50000), the line chart has a noticeable lag (up to several seconds), compared for instance to the scatter plot.

[bburlacu]

r7326: Fixed speed issue in RegressionSolutionLineChartView. The problem was an unnecessary call to the InsertEmptyPoints procedure. The MSDN website (​http://msdn.microsoft.com/en-us/library/dd456677.aspx) specifies the context in which this method is useful: when the data points have no Y value. In our case however there are no such points, so by removing the calls, performance becomes similar to the scatter plot (which also does not insert empty points) and is reasonably fast (tested on a data set with 50000 rows).

[gkronber]

I introduced the call to InsertEmptyPoints in order to fix problems with NaN values in either predicted values or original values. Please check if this still works as expected.

Please also check if everything works correctly for regression and classification ensembles (as produced for instance by CV).

[bburlacu]

r7333: Fixed series color for empty points.

Some observations after testing the chart behavior with different types of points: when calling the DataBindXY method, NaN y-values get converted and the points IsEmpty flag remains set to true:

• FastPoint and FastLine chart types convert NaN values to 0.0

• Point and Line chart types convert NaN values to the Y value of the nearest not empty neighboring point, or to the average of the left and right neighboring points (if both exist and are not empty)

By default, empty points are invisible on the chart (transparent foreground color), but this is solved by setting their color to the default series color. I attached a screenshot of this.

[bburlacu]

Chart types and empty points behavior

[bburlacu]

r7335: Also removed the InsertEmptyPoints call from inside the ToggleSeriesData method.

[bburlacu]

r7406: Fixed line chart behavior for cases when the data point series are not continuous (some indices are not consecutive).