Draw a "ladder of powers" plot, plotting each of several powers of y against the same powers of x.

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Description

Draw a "ladder of powers" plot, plotting each of several powers of y against the same powers of x. The powers are

result <- data.frame(-1/x, -1/sqrt(x), log(x), sqrt(x), x, x^2)

names(result) <- c(-1, -.5, 0, .5, 1, 2)

Usage

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ladder(formula.in, data=sys.parent(),
       main.in="Ladders of Powers",
       panel.in=panel.cartesian,
       xlab=deparse(formula.in[[3]]),
       ylab=deparse(formula.in[[2]]),
       scales=list(alternating=if.R(s=TRUE, r=FALSE),
         labels=FALSE, ticks=FALSE, cex=.6),
       par.strip.text=list(cex=.6),
       cex=.5, pch=16, between=list(x=.3, y=.3),
       dsx=xlab,
       dsy=ylab,
       ladder.function=ladder.f,
       strip.number=if.R(r=2, s=1),
       strip.names,
       strip.style=1,
       strip,
       oma=c(0,0,0,0),  ## S-Plus
       axis3.line=.61,
       layout=c(length(tmp$x.power), length(tmp$y.power)),
       axis.key.padding = 10, ## R right axis
       key.axis.padding = 10, ## R top axis
       useOuter=TRUE, ## R useOuterStrips(combineLimits(result))
       ...)

ladder3(x, y,
        dsx=deparse(substitute(x)),
        dsy=deparse(substitute(y)),
        ladder.function=ladder.f)

ladder.f(x, name.prefix="")

ladder.fstar(x, name.prefix="")

strip.ladder(which.given,
             which.panel,
             var.name,
             factor.levels,
             shingle.intervals,
             par.strip.text=trellis.par.get("add.text"),
             strip.names=c(TRUE,TRUE),
             style=1,
             ...)

Arguments

formula.in

A formula with exactly one variable on each side.

data

data.frame

main.in

main title for xyplot

panel.in

panel.cartesian has many arguments in addition to the arguments in panel.xyplot. Any replacement panel function must have those argument names, even if it doesn't do anything with them.

xlab, ylab

Trellis arguments, default to right- and left-sides of the formula.in.

strip

Strip function. Our default is strip.ladder (see below). The other viable argument value is FALSE.

cex, pch, between, scales, layout

arguments for xyplot.

dsx, dsy

Names to be used as level names in ladder.function for the generated factor distinguishing the powers. They default to xlab, ylab. For long variable names, an abbreviated name here will decrease clutter in the ladder of powers plot. These names are not visible in the plot when strip=FALSE.

ladder.function

function to use to create data.frame of powers of input variable.

name.prefix

Base name used for column names of powers. The default is empty (""). An alternative must include the power symbol "^", for example, "abc^".

strip.number

Number of strip labels in each panel of the display. 0: no strip labels; 1: one strip label of the form y^p ~ x^q; 2: two strip labels of the form ylab: y^p and xlab: x^q, where p and q are the powers returned by ladders; y and x are the arguments dsy and dsx.

useOuter

logical, defaults to TRUE. In R, this implies that strip.number is forced to 2 and that the resulting "trellis" object will be sent through
useOuterStrips(combineLimits(result)).
This argument is ignored by S-Plus.

strip.style

style argument to strip.

oma

argument to par in S-Plus.

...

other arguments to xyplot.

axis3.line

extra space to make the top axis align with the top of the top row of panels. Trial and error to choose a good value.

axis.key.padding

Extra space on right of set of panels in R.

key.axis.padding

Extra space on top of set of panels in R.

x, y

variables.

which.given, which.panel, var.name, factor.levels, shingle.intervals, par.strip.text

See strip.default.

strip.names, style

We always print the strip.names in style=1. Multicolored styles are too busy.

Details

The ladder function uses panel.cartesian which is defined differently in R (using grid graphics) and S-Plus (using traditional graphics). Therefore the fine control over appearance uses different arguments or different values for the same arguments.

Value

ladder returns a "trellis" object.

The functions ladder.fstar and ladder.f take an input vector x of non-negative values and construct a data.frame by taking the input to the powers c(-1, -.5, 0, .5, 1, 2), one column per power. ladder.f uses the simple powers and ladder.fstar uses the scaled Box–Cox transformation.

ladder.fstar ladder.fstar notation
(x^p - 1)/p (x^p - 1)/p p
(1/x - 1)/(-1) (1/x - 1)/(-1) -1.0
(1/sqrt(x)-1)/(-.5) (1/sqrt(x)-1)/(-.5) -0.5
log(x) log(x) 0.0
((sqrt(x)-1)/.5) ((sqrt(x)-1)/.5) 0.5
x-1 x-1 1.0
(x^2 - 1)/2 (x^2 - 1)/2 2.0

ladder3 takes two vectors as arguments. It returns a data.frame with five columns:

X, Y: data to be plotted. The column X contains the data from the input x taken to all the powers and aligned with the similarly expanded column Y.

x, y: symbolic labeling of the power corresponding to X,Y.

group: result from pasting the labels in x, y with * between them.

Author(s)

Richard M. Heiberger <rmh@temple.edu>

References

Heiberger, Richard M. and Holland, Burt (2004b). Statistical Analysis and Data Display: An Intermediate Course with Examples in S-Plus, R, and SAS. Springer Texts in Statistics. Springer. ISBN 0-387-40270-5.

Hoaglin, D.~C., Mosteller, F., and Tukey, J.~W., editors (1983). Understanding Robust and Exploratory Data Analysis. Wiley.

Box, G. E.~P. and Cox, D.~R. (1964). An analysis of transformations. J. Royal Statist Soc B, 26:211–252.

See Also

panel.cartesian

Examples

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data(tv)

## default
## R: outer strip labels
## S-Plus: one strip label per panel (too full for this example, see below)
ladder(life.exp ~ ppl.per.phys, data=tv,
       main="Ladder of Powers for Life Expectancy and People per Physician")

## Not run: 
## one strip label
if.R(r=ladder(life.exp ~ ppl.per.phys, data=tv, strip.number=1, useOuter=FALSE,
              dsx="ppp", dsy="le"),
     s=ladder(life.exp ~ ppl.per.phys, data=tv, strip.number=1,
              dsx="ppp", dsy="le")) ## S-Plus default

## two strip labels
if.R(r=ladder(life.exp ~ ppl.per.phys, data=tv, strip.number=2, useOuter=FALSE),
     s=ladder(life.exp ~ ppl.per.phys, data=tv, strip.number=2,
              axis3.line=1.2))

## outer strip labels
if.R(r=ladder(life.exp ~ ppl.per.phys, data=tv, useOuter=TRUE), ## R default
     s={}) ## S-Plus not available

## no strip labels (probably silly, but possible)
if.R(r=ladder(life.exp ~ ppl.per.phys, data=tv, strip.number=0, useOuter=FALSE),
     s=ladder(life.exp ~ ppl.per.phys, data=tv, strip.number=0,
              axis3.line=0))

## End(Not run)

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