R: Draw two plot series with different y scales

doubleYScale {latticeExtra}

R Documentation

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, ..., under = FALSE)

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 between 1 and 6; a value of 0 or NULL can be given to leave the default settings. These will also be applied to the y-axes and ylab, if relevant. `use.style` simply changes the defaults of the style arguments.
`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.
`under`	if TRUE, draw `obj2` under `obj1`.

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.

Value

a merged trellis object.

Author(s)

Felix Andrews felix@nfrac.org

Examples

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"))
## ...with custom styles
update(doubleYScale(obj1, obj2, text = c("obj1", "obj2")),
  par.settings = simpleTheme(col = c('red','black'), lty = 1:2))

## 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")))

[Package latticeExtra version 0.6-25 Index]