sweep
Sweep out Array Summaries
Return an array obtained from an input array by sweeping out a summary statistic.
Usage
sweep(x, MARGIN, STATS, FUN = "-", check.margin = TRUE, ...)Arguments
- x
- an array.
- MARGIN
- a vector of indices giving the extent(s) of
xwhich correspond toSTATS. - STATS
- the summary statistic which is to be swept out.
- FUN
- the function to be used to carry out the sweep.
- check.margin
- logical. If
TRUE(the default), warn if the length or dimensions ofSTATSdo not match the specified dimensions ofx. Set toFALSEfor a small speed gain when you know that dimensions match. - ...
- optional arguments to
FUN.
Details
FUN is found by a call to match.fun. As in the
default, binary operators can be supplied if quoted or backquoted.
FUN should be a function of two arguments: it will be called
with arguments x and an array of the same dimensions generated
from STATS by aperm.
The consistency check among STATS, MARGIN and x
is stricter if STATS is an array than if it is a vector.
In the vector case, some kinds of recycling are allowed without a
warning. Use sweep(x, MARGIN, as.array(STATS)) if STATS
is a vector and you want to be warned if any recycling occurs.
Value
-
An array with the same shape as
x, but with the summary
statistics swept out.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
See Also
apply on which sweep used to be based;
scale for centering and scaling.
Examples
library(base)
require(stats) # for median
med.att <- apply(attitude, 2, median)
sweep(data.matrix(attitude), 2, med.att) # subtract the column medians
## More sweeping:
A <- array(1:24, dim = 4:2)
## no warnings in normal use
sweep(A, 1, 5)
(A.min <- apply(A, 1, min)) # == 1:4
sweep(A, 1, A.min)
sweep(A, 1:2, apply(A, 1:2, median))
## warnings when mismatch
sweep(A, 1, 1:3) # STATS does not recycle
sweep(A, 1, 6:1) # STATS is longer
## exact recycling:
sweep(A, 1, 1:2) # no warning
sweep(A, 1, as.array(1:2)) # warning