R: Plot contiguous blocks along x axis.

panel.xblocks {latticeExtra}

R Documentation

Plot contiguous blocks along x axis.

Description

Plot contiguous blocks along x axis. A typical use would be to highlight events or periods of missing data.

Usage

panel.xblocks(x, ...)

## Default S3 method:
panel.xblocks(x, y, ..., col = NULL, border = NA, 
              height = unit(1, "npc"),
              block.y = unit(0, "npc"), vjust = 0,
              name = "xblocks", gaps = FALSE,
              last.step = median(diff(tail(x))))

## S3 method for class 'ts'
panel.xblocks(x, y = x, ...)
## S3 method for class 'zoo'
panel.xblocks(x, y = x, ...)

Arguments

`x, y`	In the default method, `x` gives the ordinates along the x axis and must be in increasing order. `y` gives the color values to plot as contiguous blocks. If `y` is numeric, data coverage is plotted, by converting it into a logical (`!is.na(y)`). Finally, if `y` is a function, it is applied to `x` (`time(x)` in the time series methods). If `y` has character (or factor) values, these are interpreted as colors – and should therefore be color names or hex codes. Missing values in `y` are not plotted. The default color is taken from the current theme: `trellis.par.get("plot.line")$col`. If `col` is given, this over-rides the block colors. The `ts` and `zoo` methods plot the `y` values against the time index `time(x)`.
`...`	In the default method, further arguments are graphical parameters passed on to `gpar`.
`col`	if `col` is specified, it determines the colors of the blocks defined by `y`. If multiple colors are specified they will be repeated to cover the total number of blocks.
`border`	border color.
`height`	height of blocks, defaulting to the full panel height. Numeric values are interpreted as native units.
`block.y`	y axis position of the blocks. Numeric values are interpreted as native units.
`vjust`	vertical justification of the blocks relative to `block.y`. See `grid.rect`.
`name`	a name for the grob (grid object).
`gaps`	Deprecated. Use `panel.xblocks(time(z), is.na(z))` instead.
`last.step`	width (in native units) of the final block. Defaults to the median of the last 5 time steps (assuming steps are regular).

Details

Blocks are drawn forward in "time" from the specified x locations, up until the following value. Contiguous blocks are calculated using rle.

Author(s)

Felix Andrews felix@nfrac.org

Examples

## Example of highlighting peaks in a time series.
set.seed(0)
flow <- ts(filter(rlnorm(200, mean = 1), 0.8, method = "r"))

## using an explicit panel function
xyplot(flow, panel = function(x, y, ...) {
  panel.xblocks(x, y > mean(y), col = "lightgray")
  panel.xyplot(x, y, ...)
})
## using layers; this is the `ts` method because `>` keeps it as ts.
xyplot(flow) +
  layer_(panel.xblocks(flow > mean(flow), col = "lightgray"))

## Example of alternating colors, here showing calendar months
flowdates <- as.Date("2000-01-01") + as.numeric(time(flow))
xyplot(flow ~ flowdates, type = "l") +
  layer_(panel.xblocks(x, months,
         col = c("lightgray", "#e6e6e6"), border = "darkgray"))

## highlight values above and below thresholds.
## blue, gray, red colors:
rgb <- hcl(c(0, 0, 260), c = c(100, 0, 100), l = c(90, 90, 90))
xyplot(flow) +
  layer_(panel.xblocks(time(flow),
         cut(flow, c(0,15,30,Inf), labels = rgb)))

## Example of highlighting gaps (NAs) in time series.
## set up example data
z <- ts(cbind(A = 0:5, B = c(6:7, NA, NA, 10:11), C = c(NA, 13:17)))

## show data coverage only (highlighting gaps)
xyplot(z, panel = panel.xblocks,
       scales = list(y = list(draw = FALSE)))

## draw gaps in darkgray
xyplot(z, type = c("p","s")) +
  layer_(panel.xblocks(x, is.na(y), col = "darkgray"))

## Example of overlaying blocks from a different series.
## Are US presidential approval ratings linked to sunspot activity?
## Set block height, default justification is along the bottom.
xyplot(presidents) + layer(panel.xblocks(sunspot.year > 50, height = 2))

[Package latticeExtra version 0.6-25 Index]