The XYINTERP function converts an XY graph into a standard interval series by linearly interpolating an XY graph.
linearly interpolates the XY graph in W3 using the smallest x interval of W3 as the interpolation increment. In order to interpolate, the x values of the XY graph must be monotonic (i.e., steadily increasing or decreasing). DADiSP cannot interpolate XY graphs that look like circles.
XYINTERP also accepts an interpolation interval, so:
interpolates W3 with an interval of 0.125. Once you have interpolated an XY graph, you can operate on it with any DADiSP function.
Also, RESAMPLE supports several different methods of interpolating irregularly spaced data to regularly spaced data.