Plot spline

Usage: plot spline x1 y1 x2 y2 ... (normal mode)

      plot spline [[x] y1...]         (list mode)

Normal mode: The command draws a cubic spline through the given points. The spline starts at the first point and ends at the last point with vanishing second derivative. The x-values must be strictly increasing.

List mode: The command draws draws cubic spline curves through the points of the given vector expressions x, y1,... If no vector expressions are specified, splines are drawn through the points of all list columns. If the x-expression is omitted (i.e. if only a single expression, y1, is given), the x-coordinates are taken from the x-column of the list.