# invTranPlot

From car v2.0-20
by John Fox

##### 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.

##### See Also

##### 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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