# TransformationAxes

From car v2.0-20
by John Fox

##### Axes for Transformed Variables

These functions produce axes for the original scale of
transformed variables. Typically these would appear as additional
axes to the right or
at the top of the plot, but if the plot is produced with
`axes=FALSE`

, then these functions could be used for axes below or to
the left of the plot as well.

- Keywords
- aplot

##### Usage

```
basicPowerAxis(power, base=exp(1),
side=c("right", "above", "left", "below"),
at, start=0, lead.digits=1, n.ticks, grid=FALSE, grid.col=gray(0.50),
grid.lty=2,
axis.title="Untransformed Data", cex=1, las=par("las"))
bcPowerAxis(power, side=c("right", "above", "left", "below"),
at, start=0, lead.digits=1, n.ticks, grid=FALSE, grid.col=gray(0.50),
grid.lty=2,
axis.title="Untransformed Data", cex=1, las=par("las"))
yjPowerAxis(power, side=c("right", "above", "left", "below"),
at, lead.digits=1, n.ticks, grid=FALSE, grid.col=gray(0.50),
grid.lty=2,
axis.title="Untransformed Data", cex=1, las=par("las"))
probabilityAxis(scale=c("logit", "probit"),
side=c("right", "above", "left", "below"),
at, lead.digits=1, grid=FALSE, grid.lty=2, grid.col=gray(0.50),
axis.title = "Probability", interval = 0.1, cex = 1, las=par("las"))
```

##### Arguments

- power
- power for Box-Cox, Yeo-Johnson, or simple power transformation.
- scale
- transformation used for probabilities,
`"logit"`

(the default) or`"probit"`

. - side
- side at which the axis is to be drawn; numeric
codes are also permitted:
`side = 1`

for the bottom of the plot,`side=2`

for the left side,`side = 3`

for the top,`side = 4`

for the right side. - at
- numeric vector giving location of tick marks on original scale; if missing, the function will try to pick nice locations for the ticks.
- start
- if a
*start*was added to a variable (e.g., to make all data values positive), it can now be subtracted from the tick labels. - lead.digits
- number of leading digits for determining `nice' numbers
for tick labels (default is
`1`

. - n.ticks
- number of tick marks; if missing, same as corresponding transformed axis.
- grid
- if
`TRUE`

grid lines for the axis will be drawn. - grid.col
- color of grid lines.
- grid.lty
- line type for grid lines.
- axis.title
- title for axis.
- cex
- relative character expansion for axis label.
- las
- if
`0`

, ticks labels are drawn parallel to the axis; set to`1`

for horizontal labels (see`par`

). - base
- base of log transformation for
`power.axis`

when`power = 0`

. - interval
- desired interval between tick marks on the probability scale.

##### Details

The transformations corresponding to the three functions are as follows:
[object Object],[object Object],[object Object],[object Object]
These functions will try to place tick marks at reasonable locations, but
producing a good-looking graph sometimes requires some fiddling with the
`at`

argument.

##### Value

- These functions are used for their side effects: to draw axes.

##### References

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

##### See Also

##### Examples

```
UN <- na.omit(UN)
par(mar=c(5, 4, 4, 4) + 0.1) # leave space on right
with(UN, plot(log(gdp, 10), log(infant.mortality, 10)))
basicPowerAxis(0, base=10, side="above",
at=c(50, 200, 500, 2000, 5000, 20000), grid=TRUE,
axis.title="GDP per capita")
basicPowerAxis(0, base=10, side="right",
at=c(5, 10, 20, 50, 100), grid=TRUE,
axis.title="infant mortality rate per 1000")
with(UN, plot(bcPower(gdp, 0), bcPower(infant.mortality, 0)))
bcPowerAxis(0, side="above",
grid=TRUE, axis.title="GDP per capita")
bcPowerAxis(0, side="right",
grid=TRUE, axis.title="infant mortality rate per 1000")
with(UN, qqPlot(logit(infant.mortality/1000)))
probabilityAxis()
with(UN, qqPlot(qnorm(infant.mortality/1000)))
probabilityAxis(at=c(.005, .01, .02, .04, .08, .16), scale="probit")
```

*Documentation reproduced from package car, version 2.0-20, License: GPL (>= 2)*

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