This option generates a cubic spline connection. To use the connection, the X values must be discrete and increasing. Furthermore, the number of data points cannot exceed 900 (if the data set exceeds this number, the operation will fail).

Since curvature information is held in memory, the spline resolution remains the same regardless of page magnification. The SplineStep variable in the ORIGIN.INI file controls the spline calculation increment. It is expressed in units of .1 point.

For a pair of data sets Origin makes a smooth curve using a cubic B-spline connection. The B-spline curve can be described by parametric equations. The coordinates are calculated around each point letting t range from 0 to 1. This cubic B-spline curve is continuous up to a second order derivative. Unlike spline curves which pass through the original data points , the B-spline curve winds around the original data points without passing through them. (Origin duplicates the first and last data points so the curve passes through them.)

Note: One advantage of the B-spline connection is that it does not have any requirements for the original data points, whereas the spline connection requires that the X coordinates by strictly increasing.