# invTranPlot

0th

Percentile

##### Choose a Predictor Transformation Visually or Numerically

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

Keywords
hplot, regression
##### Usage
invTranPlot(x, ...)

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

## S3 method for class 'default':
invTranPlot(x, y, lambda=c(-1, 0, 1), robust=FALSE,
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 = "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, robust=FALSE)
##### 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.
robust
If TRUE, then the estimated transformation is computed using Huber M-estimation with the MAD used to estimate scale and k=1.345. The default 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, or if robust=TRUE, 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 $\lambda$ in the first column, and the residual sum of squares from the regression for that $\lambda$ 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.

##### References

Fox, J. and Weisberg, S. (2011) An R Companion to Applied Regression, Second Edition, Sage. Pendergast, L, and Sheather, S. (in press). On sensitivity of response plot estimation of a robust estimation approach. Scandinavian Journal of Statistics. Weisberg, S. (2014) Applied Linear Regression, Fourth Edition, Wiley Wiley.

inverseResponsePlot,optimize

##### Aliases
• invTranPlot
• invTranPlot.default
• invTranPlot.formula
• invTranEstimate
##### Examples
with(UN, invTranPlot(gdp, infant.mortality))
with(UN, invTranEstimate(gdp, infant.mortality))
Documentation reproduced from package car, version 2.0-20, License: GPL (>= 2)

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