Hello Michal,

The only true “Area” series that will fill the area below a line that exists in the Infragistics for WPF toolset requires the usage of a CategoryXAxis and NumericYAxis, and from the screenshot you have provided, it appears that you are using a NumericXAxis and NumericYAxis and what I imagine is a ScatterLineSeries. Unfortunately, there does not exist a built-in “area” series for usage with the NumericX and NumericY axes at the moment, but there are is an alternative recommendation I can make in this case.

My recommendation is to use a separate ScatterPolygonSeries and make a shape that fits inside of the ScatterLineSeries that you have plotted. The points would essentially correspond to the points in your ScatterLineSeries, and this should allow you to place a “fill” inside of the area to the left of your line. Please note that the start and end points would need to be at least at the minimum X-value of the NumericXAxis in this case. You can read further about the ScatterPolygonSeries here: https://es.infragistics.com/help/wpf/datachart-scatter-polygon-series.

If you would like to see a NumericX / NumericY axis area series potentially implemented in a future version of the XamDataChart control in the Infragistics for WPF toolset, I would recommend suggesting a new product idea for it at our WPF Ideas Site, here. This will place you in direct communication with our product management teams who plan and prioritize upcoming features and development based on community and user feedback.

Please let me know if you have any other questions or concerns on this matter.