The demo shows a Scatter Line series in RadHtmlChart, which is useful for displaying numerical data.
Spline (Smooth) and normal appearance of the series can be configured via the
LineStyle property in the LineAppearance tag since Q1 2014
by choosing one of the options from the LineStyle enumeration:
Normal — the default series appearance.
Smooth — the series items are connected with a fitted curve which represents a rough approximation of the missing data points.