type = key

Specify the interpolation method. key is either “lin” (linear, default), “log” (log-linear), “cs” (Cardinal spline), “cr” (Catmull-Rom spline), “cb” (Cubic spline), “lcs” (log-cardinal spline), “lcr” (log-Catmull-Rom spline), or “lcb” (log-cubic spline).

tension = number

Sets the tension parameter for the Cardinal spline method of interpolation. number should be a number between 0 and 1.

f = arg (default = “actual”)

Out-of-sample fill behavior: “actual” (fill observations

outside the interpolated sample with values from the source series). “na” (fill observations outside the sample with missing values”

prompt

Force the dialog to appear from within a program.