sortedXyData               package:nls               R Documentation

Create a sortedXyData object

Description:

     This is a constructor function for the class of `sortedXyData'
     objects.  These objects are mostly used in the `initial' function
     for a self-starting nonlinear regression model, which will be of
     the `selfStart' class.

Usage:

     sortedXyData(x, y, data)

Arguments:

       x: a numeric vector or an expression that will evaluate in
          `data' to a numeric vector 

       y: a numeric vector or an expression that will evaluate in
          `data' to a numeric vector 

    data: an optional data frame in which to evaluate expressions for
          `x' and `y', if they are given as expressions 

Value:

     A `sortedXyData' object. This is a data frame with exactly two
     numeric columns, named `x' and `y'.  The rows are sorted so the
     `x' column is in increasing order.  Duplicate `x' values are
     eliminated by averaging the corresponding `y' values.

Author(s):

     Jose Pinheiro and Douglas Bates

See Also:

     `selfStart', `NLSstClosestX', `NLSstLfAsymptote',
     `NLSstRtAsymptote'

Examples:

     data( DNase )
     DNase.2 <- DNase[ DNase$Run == "2", ]
     sortedXyData( expression(log(conc)), expression(density), DNase.2 )

