Working with NOV Chart – Using Series Labels

Having accurate and complete output labels across a representative data set is a fundamental requirement for any visual data representation. A good charting product must support an automatic data label layout. This white paper outlines the usage and benefits of the automatic layout functionality.

All types of charts support automatic Data Label Layout. It is performed in two stages that can work independently or in combination. By default, both layout stages are disabled. They are activated on a per-chart basis, so all data point labels displayed in a given chart are subject to the automatic layout.

The first layout stage is called Initial Positioning. Initial Positioning aims to select a position for each label from a set of proposed locations situated around the origin point of the label. The control determines the location that causes minimum potential conflicts with other label locations.

It can be enabled with the following code:

We can continue with the label adjustment.

Label Adjustment removes overlaps by shifting the overlapping labels apart from each other, using a force-directed layout algorithm. The functionality of label adjustment can be used regardless of whether initial positioning is enabled or not. Label adjustment cannot be disabled per series basis - it applies to all data labels in the chart.

And finally, the last touch is setting the data point safeguard. Data Point Safeguard is necessary functionality since it protects the data points from being too close to each other. It can be enabled or disabled on a per series basis with the following code:

// enable the data point safeguard
m_Area.LabelLayout.EnableDataPointSafeguard = true;

In addition, you can specify the distance around the labels by using the DataPointSafeguardSize property.

// set safeguard size
m_Area.LabelLayout.DataPointSafeguardSize = new NSize(2,2);

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