zoo (version 1.7-10)

rollmean: Rolling Means/Maximums/Medians

Description

Generic functions for computing rolling means, maximums and medians of ordered observations.

Usage

rollmean(x, k, fill = if (na.pad) NA, na.pad = FALSE, 
	align = c("center", "left", "right"), ...)
rollmeanr(..., align = "right")
rollmax(x, k, fill = if (na.pad) NA, na.pad = FALSE, 
	align = c("center", "left", "right"), ...)
rollmaxr(..., align = "right")
rollmedian(x, k, fill = if (na.pad) NA, na.pad = FALSE, 
	align = c("center", "left", "right"), ...)
rollmedianr(..., align = "right")
rollsum(x, k, fill = if (na.pad) NA, na.pad = FALSE, 
	align = c("center", "left", "right"), ...)
rollsumr(..., align = "right")

Arguments

x

an object (representing a series of observations).

k

integer width of the rolling window. Must be odd for rollmedian.

fill

a three-component vector or list (recycled otherwise) providing filling values at the left/within/to the right of the data range. See the fill argument of na.fill for details.

na.pad

deprecated. Use fill = NA instead of na.pad = TRUE.

align

character specifying whether the index of the result should be left- or right-aligned or centered (default) compared to the rolling window of observations.

...

Further arguments passed to methods.

Value

• An object of the same class as x with the rolling mean/max/median.

Details

These functions compute rolling means, maximums and medians respectively and are thus similar to rollapply but are optimized for speed.

Currently, there are methods for "zoo" and "ts" series and default methods. The default method of rollmedian is an interface to runmed. The default method of rollmean does not handle inputs that contain NAs. In such cases, use rollapply instead.

See Also

rollapply, zoo, na.fill

Examples

x.Date <- as.Date(paste(2004, rep(1:4, 4:1), sample(1:28, 10), sep = "-"))
x <- zoo(rnorm(12), x.Date)

rollmean(x, 3)
rollmax(x, 3)
rollmedian(x, 3)

xm <- zoo(matrix(1:12, 4, 3), x.Date[1:4])
rollmean(xm, 3)
rollmax(xm, 3)
rollmedian(xm, 3)

rollapply(xm, 3, mean) # uses rollmean
rollapply(xm, 3, function(x) mean(x)) # does not use rollmean