SYNOPSIS

fn spline.4 [+s|-s] [[n=]npts] [f=from] [t=to]

DESCRIPTION

The function spline.4 creates data points at evenly spaced intervals using a cubic spline algorithm to interpolate new points from the old. The interpolated points lie on a cubic polynomial between each pair of original points. Each polynomial section is joined continuously with the next via continuous first and second derivatives.

The default from and to values are the first and last values of x in the original data. If you don't enter any arguments, you will be prompted for the number of points and the range to interpolate over.

The +s and \-s options turn the sorting and merging of data actions on and off. Data must be in increasing order, by x, for the spline to succeed. Also, x values must be distinct. Turning the sort off saves time for splining presorted data. The default is no sort.

The spline.4 function turns off error-bar mode, and error-bar values are set to zero.