Plot contiguous blocks along x axis.

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

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 rectGrob.

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

Felix Andrews felix@nfrac.org

See also

xyplot.ts, panel.rect, grid.rect

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:
bgr <- hcl(c(0, 0, 260), c = c(100, 0, 100), l = c(90, 90, 90))
dflow <- cut(flow, c(0,15,30,Inf), labels = bgr)
xyplot(flow) + layer_(panel.xblocks(time(flow), dflow))


## 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))