place.knots               package:mgcv               R Documentation

Automatically place a set of knots evenly through covariate values

Description:

     Given a univariate array of covariate values, places a set of
     knots for a regressin spline evenly through the  covariate values.

Usage:

      place.knots(x,nk)

Arguments:

       x: array of covariate values (need not be sorted).

      nk: integer indicating the required number of knots.

Details:

     Places knots evenly throughout a set of covariates. For example,
     if you had 11 covariate values and wanted 6 knots  then a knot
     would be placed at the first (sorted) covariate value and every
     second (sorted) value thereafter. With  less convenient numbers of
     data and knots the knots are placed within intervals between data
     in order to achieve  even coverage, where even means having
     approximately the same number of data between each pair of knots.

Value:

     An array of knot locations.

Author(s):

     Simon N. Wood simon@stats.gla.ac.uk

References:

     <URL: http://www.stats.gla.ac.uk/~simon/>

See Also:

     'smooth.construct.cc.smooth.spec'

Examples:

     x<-runif(30)
     place.knots(x,7)
     rm(x)

