Hi Dennis,
Please have in mind that null, empty,
negative, and zero values have no effect when calculating ratios. For this reason, these values should not be used with pie chart . If you want to visually indicate such values in a chart, change the chart type to be something other than pie.
Displaying the values as positive but giving negative labels for them is not recommended from our side as well. However if you want, you can easily achieve this by using the
ItemLabelFormat property of the PieSeriesDefinition. In your case you need to specify the following format:
ItemLabelFormat =
"-#Y". The #Y token is a place holder for the value of the data point. For more information on using the standard .NET formats and the custom RadChart formats visit the Format Expressions help topic.
I hope this helps.
All the best,
Petar Kirov
the Telerik team