cut {base} | R Documentation |
cut
divides the range of x
into intervals
and codes the values in x
according to which
interval they fall.
The leftmost interval corresponds to level one,
the next leftmost to level two and so on.
cut(x, ...) ## Default S3 method: cut(x, breaks, labels = NULL, include.lowest = FALSE, right = TRUE, dig.lab = 3, ...)
x |
a numeric vector which is to be converted to a factor by cutting. |
breaks |
either a numeric vector of cut points or number
giving the number of intervals which x is to be cut into. |
labels |
labels for the levels of the resulting category. By default,
labels are constructed using "(a,b]" interval notation. If
labels = FALSE , simple integer codes are returned instead of
a factor. |
include.lowest |
logical, indicating if an ‘x[i]’ equal to
the lowest (or highest, for right = FALSE ) ‘breaks’
value should be included. |
right |
logical, indicating if the intervals should be closed on the right (and open on the left) or vice versa. |
dig.lab |
integer which is used when labels are not given. It determines the number of digits used in formatting the break numbers. |
... |
further arguments passed to or from other methods. |
If a labels
parameter is specified, its values are used
to name the factor levels. If none is specified, the factor
level labels are constructed as "(b1, b2]"
, "(b2, b3]"
etc. for right = TRUE
and as "[b1, b2)"
, ... if
right = FALSE
.
In this case, dig.lab
indicates the minimum number of digits
should be used in formatting the numbers b1
, b2
, ....
A larger value (up to 12) will be used if needed to distinguish
between any pair of endpoints: if this fails labels such as
"Range3"
will be used.
A factor
is returned, unless labels = FALSE
which
results in the mere integer level codes.
Instead of table(cut(x, br))
, hist(x, br, plot = FALSE)
is
more efficient and less memory hungry. Instead of cut(*,
labels = FALSE)
, findInterval()
is more efficient.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
split
for splitting a variable according to a group factor;
factor
, tabulate
, table
,
findInterval()
.
Z <- rnorm(10000) table(cut(Z, br = -6:6)) sum(table(cut(Z, br = -6:6, labels=FALSE))) sum( hist (Z, br = -6:6, plot=FALSE)$counts) cut(rep(1,5),4)#-- dummy tx0 <- c(9, 4, 6, 5, 3, 10, 5, 3, 5) x <- rep(0:8, tx0) stopifnot(table(x) == tx0) table( cut(x, b = 8)) table( cut(x, br = 3*(-2:5))) table( cut(x, br = 3*(-2:5), right = FALSE)) ##--- some values OUTSIDE the breaks : table(cx <- cut(x, br = 2*(0:4))) table(cxl <- cut(x, br = 2*(0:4), right = FALSE)) which(is.na(cx)); x[is.na(cx)] #-- the first 9 values 0 which(is.na(cxl)); x[is.na(cxl)] #-- the last 5 values 8 ## Label construction: y <- rnorm(100) table(cut(y, breaks = pi/3*(-3:3))) table(cut(y, breaks = pi/3*(-3:3), dig.lab=4)) table(cut(y, breaks = 1*(-3:3), dig.lab=4)) # extra digits don't "harm" here table(cut(y, breaks = 1*(-3:3), right = FALSE)) #- the same, since no exact INT! ## sometimes the default dig.lab is not enough to be avoid confusion: aaa <- c(1,2,3,4,5,2,3,4,5,6,7) cut(aaa, 3) cut(aaa, 3, dig.lab=4)