sortedXyData 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)

José Pinheiro and Douglas Bates

See Also

selfStart, NLSstClosestX, NLSstLfAsymptote, NLSstRtAsymptote

Examples

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