Polytransform

Purpose

Add new variables to a dataset object or matrix formed as power transforms and cross terms of the original variables.

Synopsis

yi = polyinterp(x,y,xi,width,order,deriv);

[DSOout, model] = polytransform(x, options);

Description

Estimates yi which is the smoothed values of y at the points in the vector x. (If the points are evenly spaced use the SAVGOL function instead.)

Inputs

• y = (M by N) matrix. Note that (y) is a matrix of ROW vectors to be smoothed.

• x = (1 by N) corresponding axis vector at the points at which (y) is given.

Optional Inputs

• xi = a vector of points to interpolate to.

• width = specifies the number of points in the filter {default = 15}.

• order = the order of the polynomial {default = 2}.

• deriv = the derivative {default = 0}.

Examples

If y is a 5 by 100 matrix, x is a 1 by 100 vector, and xi is a 1 by 91 vector then:

polyinterp(x,y,xi,11,3,1)

gives the 5 by 91 matrix of first-derivative row vectors resulting from an 11-point cubic interpolation to the 91 points in xi.