sortedXyData {stats} | 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 )

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