doubleYScale: Draw two plot series with different y scales

Description

Overplot two trellis objects with different y scales, optionally in different styles, adding a second y axis, and/or a second y axis label. Note: drawing plots with multiple scales is often a bad idea as it can be misleading.

Usage

doubleYScale(obj1, obj2, use.style = TRUE,
             style1 = if (use.style) 1, style2 = if (use.style) 2,
             add.axis = TRUE, add.ylab2 = FALSE,
             text = NULL, auto.key = if (!is.null(text))
               list(text, points = points, lines = lines, ...),
             points = FALSE, lines = TRUE, ...)

Arguments

obj1, obj2

trellis objects. Note that most settings, like main/sub/legend/etc are taken only from obj1; only the panel, axis and ylab are taken from obj2.

use.style, style1, style2

style1 and style2 give the `group number' for obj1 and obj2 respectively. The style is taken from these indices into the values of trellis.par.get("superpose.line"). Therefore these should be integers

add.axis

if TRUE, draw a second y axis (for the obj2 series) on the right side of the plot.

add.ylab2

if TRUE, draw a second y axis label (from obj2$ylab) on the right side of the plot. Note, this will replace any existing key or legend on the right side, i.e. with space = "right".

text, auto.key, points, lines, ...

if non-NULL, add a key to the display, using entries named by text. Further arguments are passed on to simpleKey at plot time.

Value

a merged trellis object.

Details

Panels from the trellis object obj2 will be drawn in the corresponding panel of obj1. Axis settings are taken from the trellis objects, so most scales arguments such as draw, at, labels etc from obj2 will carry over to the second y axis.

Examples

Run this code

set.seed(1)
foo <- list(x = 1:100, y = cumsum(rnorm(100)))
## show original data
xyplot(y + y^2 ~ x, foo, type = "l")
## construct separate plots for each series
obj1 <- xyplot(y ~ x, foo, type = "l")
obj2 <- xyplot(y^2 ~ x, foo, type = "l")
## simple case: no axis for the overlaid plot
doubleYScale(obj1, obj2, add.axis = FALSE)
## draw second y axis
doubleYScale(obj1, obj2)
## ...with second ylab
doubleYScale(obj1, obj2, add.ylab2 = TRUE)
## ...or with a key
doubleYScale(obj1, obj2, text = c("obj1", "obj2"))

## different plot types
x <- rnorm(60)
doubleYScale(histogram(x), densityplot(x), use.style = FALSE)
## (but see ?as.layer for a better way to do this)

## multi-panel example
## a variant of Figure 5.13 from Sarkar (2008)
## http://lmdvr.r-forge.r-project.org/figures/figures.html?chapter=05;figure=05_13
data(SeatacWeather)
temp <- xyplot(min.temp + max.temp ~ day | month,
               data = SeatacWeather, type = "l", layout = c(3, 1))
rain <- xyplot(precip ~ day | month, data = SeatacWeather, type = "h")

doubleYScale(temp, rain, style1 = 0, style2 = 3, add.ylab2 = TRUE,
   text = c("min. T", "max. T", "rain"), columns = 3)

## re-plot with different styles
update(trellis.last.object(),
   par.settings = simpleTheme(col = c("black", "red", "blue")))