R: Choose a Predictor Transformation Visually or Numerically

invTranPlot {car}

R Documentation

Choose a Predictor Transformation Visually or Numerically

Description

invTranPlot draws a two-dimensional scatterplot of Y versus X, along with the OLS fit from the regression of Y on (Y^(lam)-1)/lam. invTranEstimate finds the nonlinear least squares estimate of lambda and its standard error.

Usage

            
invTranPlot(x, ...)

## S3 method for class 'formula'
invTranPlot(x, data, subset, na.action, ...)

## Default S3 method:
invTranPlot(x, y, lambda=c(-1, 0, 1), 
        lty.lines=rep(c("solid", "dashed", "dotdash", "longdash", "twodash"), 
        length=1 + length(lambda)), lwd.lines=2, 
        col=palette()[1], col.lines=palette(),
        xlab=deparse(substitute(x)), ylab=deparse(substitute(y)),
        family="bcPower", optimal=TRUE, key="auto",
        id.method = abs(residuals(lm(y~x))),
        labels, 
        id.n = if(id.method[1]=="identify") Inf else 0,
        id.cex=1, id.col=palette()[1], grid=TRUE, ...)

invTranEstimate(x, y, family="bcPower", confidence=0.95)

Arguments

`x`	The predictor variable, or a formula with a single response and a single predictor
`y`	The response variable
`data`	An optional data frame to get the data for the formula
`subset`	Optional, as in `lm`, select a subset of the cases
`na.action`	Optional, as in `lm`, the action for missing data
`lambda`	The powers used in the plot. The optimal power than minimizes the residual sum of squares is always added unless optimal is `FALSE`.
`family`	The transformation family to use, `"bcPower"`, `"yjPower"`, or a user-defined family.
`confidence`	returns a profile likelihood confidence interval for the optimal transformation with this confidence level. If `FALSE`, no interval is returned.
`optimal`	Include the optimal value of lambda?
`lty.lines`	line types corresponding to the powers
`lwd.lines`	the width of the plotted lines, defaults to 2 times the standard
`col`	color(s) of the points in the plot. If you wish to distinguish points according to the levels of a factor, we recommend using symbols, specified with the `pch` argument, rather than colors.
`col.lines`	color of the fitted lines corresponding to the powers. The default is to use the colors returned by `palette`
`key`	The default is `"auto"`, in which case a legend is added to the plot, either above the top marign or in the bottom right or top right corner. Set to NULL to suppress the legend.
`xlab`	Label for the horizontal axis.
`ylab`	Label for the vertical axis.
`id.method,labels,id.n,id.cex,id.col`	Arguments for the labelling of points. The default is `id.n=0` for labeling no points. See `showLabels` for details of these arguments.
`...`	Additional arguments passed to the plot method, such as `pch`.
`grid`	If TRUE, the default, a light-gray background grid is put on the graph

Value

invTranPlot plots a graph and returns a data frame with lam in the first column, and the residual sum of squares from the regression for that lam in the second column.

invTranEstimate returns a list with elements lambda for the estimate, se for its standard error, and RSS, the minimum value of the residual sum of squares.

Author(s)

Sanford Weisberg, sandy@stat.umn.edu

References

Fox, J. and Weisberg, S. (2011) An R Companion to Applied Regression, Second Edition, Sage.

Weisberg, S. (2005) Applied Linear Regression, Third Edition. Wiley.

Examples

with(UN, invTranPlot(gdp, infant.mortality))
with(UN, invTranEstimate(gdp, infant.mortality))

[Package car version 2.0-12 Index]