as.layer {latticeExtra} | R Documentation

## Overlay panels of Trellis plots on same or different scales

### Description

Allows overlaying of Trellis plots, drawn on the same scales or on different scales in each of the x and y dimensions. There are options for custom axes and graphical styles.

### Usage

    as.layer(x, ...)

    ## S3 method for class 'trellis'
    as.layer(x, x.same = TRUE, y.same = TRUE,
             axes = c(if (!x.same) "x", if (!y.same) "y"), opposite = TRUE,
             outside = FALSE, theme = x$par.settings, ...)

### Arguments

`x` | a trellis object.
`x.same` | retains the existing panel x scale for the new layer, rather than using the layer's native x scale.
`y.same` | retains the existing panel y scale.
`axes` | which of the axes to draw (`NULL` for neither). Axes might not be drawn anyway, such as if `scales$draw == FALSE`.
`opposite` | whether to draw axes on the opposite side to normal: that is, the top and/or right sides rather than bottom and/or left. May be a vector of length 2 to specify for x and y axes separately.
`outside` | whether to draw the axes outside the plot region. Note that space for outside axes will not be allocated automatically. May be a vector of length 2 to specify for x and y axes separately.
`theme` | passed to `layer`.
`...` | passed to `layer`: typically the `style` argument would be specified.

### Details

Panels from the trellis object `x` will be drawn in the corresponding panel of another trellis object, so packet numbers match (see examples).

Axis setting are taken from the trellis object `x`, so most `scales` arguments such as `draw`, `at`, `labels` etc will carry over to the overlaid axes. Only the main axis settings are used (i.e. left or bottom), even when `opposite = TRUE`.

Currently, outside top axes will be drawn in the strip if there are strips.

### Value

an updated trellis object.

### Author(s)

Felix Andrews felix@nfrac.org

### See Also

`doubleYScale`, `layer`, `panel.axis`

### Examples

    b1 <- barley
    b2 <- barley
    b2$yield <- b2$yield + 10

    ## panels are matched up by packet number
    dotplot(variety ~ yield | site * year, b1) +
      as.layer(dotplot(variety ~ yield | site * year, b2, col = "red"))

    ## which gives the same result as:
    dotplot(variety ~ yield | site * year, data = b1, subscripts = TRUE) +
      layer(panel.dotplot(yield[subscripts], variety[subscripts], col = "red"),
            data = b2)

    ## example with all same scales (the default):
    xyplot(fdeaths ~ mdeaths) +
      as.layer(xyplot(fdeaths ~ mdeaths, col = 2, subset = ldeaths > 2000))

    ## same x scales, different y scales:
    xyplot(fdeaths ~ mdeaths) +
      as.layer(bwplot(~ mdeaths, box.ratio = 0.2), y.same = FALSE)

    ## same y scales, different x scales:
    xyplot(fdeaths ~ mdeaths) +
      as.layer(bwplot(fdeaths ~ factor(mdeaths*0), box.ratio = 0.2), x.same = FALSE)

    ## as.layer() is called automatically if two plots are added:
    histogram(~ ldeaths, type = "density") + densityplot(~ ldeaths, lwd = 3)

    ## applying one panel layer to several panels of another object
    xyplot(Sepal.Length + Sepal.Width ~ Petal.Length + Petal.Width | Species,
           data = iris, scales = "free") +
       as.layer(levelplot(volcano), x.same = FALSE, y.same = FALSE, under = TRUE)

[Package latticeExtra version 0.6-28 Index]