Description
table
uses the cross-classifying factors to build a contingency table of the counts at each combination of factor levels.
Usage
table(…, exclude = if (useNA == "no") c(NA, NaN), useNA = c("no", "ifany", "always"), dnn = list.names(…), deparse.level = 1)as.table(x, …)is.table(x)
# S3 method for tableas.data.frame(x, row.names = NULL, …, responseName = "Freq", stringsAsFactors = TRUE, sep = "", base = list(LETTERS))
Arguments
…
one or more objects which can be interpreted as factors (including character strings), or a list (or data frame) whose components can be so interpreted. (For as.table
, arguments passed to specific methods; for as.data.frame
, unused.)
exclude
levels to remove for all factors in …
. If it does not contain NA
and useNA
is not specified, it implies useNA = "ifany"
. See ‘Details’ for its interpretation for non-factor arguments.
useNA
whether to include NA
values in the table. See ‘Details’. Can be abbreviated.
dnn
the names to be given to the dimensions in the result (the dimnames names).
deparse.level
controls how the default dnn
is constructed. See ‘Details’.
x
an arbitrary R object, or an object inheriting from class "table"
for the as.data.frame
method. Note that as.data.frame.table(x, *)
may be called explicitly for non-table x
for “reshaping” array
s.
row.names
a character vector giving the row names for the data frame.
responseName
The name to be used for the column of table entries, usually counts.
stringsAsFactors
logical: should the classifying factors be returned as factors (the default) or character vectors?
sep, base
passed to provideDimnames
.
Value
table()
returns a contingency table, an object of class "table"
, an array of integer values. Note that unlike S the result is always an array
, a 1D array if one factor is given.
as.table
and is.table
coerce to and test for contingency table, respectively.
The as.data.frame
method for objects inheriting from class "table"
can be used to convert the array-based representation of a contingency table to a data frame containing the classifying factors and the corresponding entries (the latter as component named by responseName
). This is the inverse of xtabs
.
Details
If the argument dnn
is not supplied, the internal function list.names
is called to compute the ‘dimname names’. If the arguments in …
are named, those names are used. For the remaining arguments, deparse.level = 0
gives an empty name, deparse.level = 1
uses the supplied argument if it is a symbol, and deparse.level = 2
will deparse the argument.
Only when exclude
is specified (i.e., not by default) and non-empty, will table
potentially drop levels of factor arguments.
useNA
controls if the table includes counts of NA
values: the allowed values correspond to never ("no"
), only if the count is positive ("ifany"
) and even for zero counts ("always"
). Note the somewhat “pathological” case of two different kinds of NA
s which are treated differently, depending on both useNA
and exclude
, see d.patho
in the ‘Examples:’ below.
Both exclude
and useNA
operate on an “all or none” basis. If you want to control the dimensions of a multiway table separately, modify each argument using factor
or addNA
.
Non-factor arguments a
are coerced via factor(a, exclude=exclude)
. Since R 3.4.0, care is taken not to count the excluded values (where they were included in the NA
count, previously).
The summary
method for class "table"
(used for objects created by table
or xtabs
) which gives basic information and performs a chi-squared test for independence of factors (note that the function chisq.test
currently only handles 2-d tables).
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
See Also
tabulate
is the underlying function and allows finer control.
Use ftable
for printing (and more) of multidimensional tables. margin.table
, prop.table
, addmargins
.
addNA
for constructing factors with NA
as a level.
xtabs
for cross tabulation of data frames with a formula interface.
Examples
# NOT RUN {require(stats) # for rpois and xtabs## Simple frequency distributiontable(rpois(100, 5))## Check the design:with(warpbreaks, table(wool, tension))table(state.division, state.region)# simple two-way contingency tablewith(airquality, table(cut(Temp, quantile(Temp)), Month))a <- letters[1:3]table(a, sample(a)) # dnn is c("a", "")table(a, sample(a), deparse.level = 0) # dnn is c("", "")table(a, sample(a), deparse.level = 2) # dnn is c("a", "sample(a)")## xtabs() <-> as.data.frame.table() :UCBAdmissions ## already a contingency tableDF <- as.data.frame(UCBAdmissions)class(tab <- xtabs(Freq ~ ., DF)) # xtabs & table## tab *is* "the same" as the original table:all(tab == UCBAdmissions)all.equal(dimnames(tab), dimnames(UCBAdmissions))a <- rep(c(NA, 1/0:3), 10)table(a) # does not report NA'stable(a, exclude = NULL) # reports NA'sb <- factor(rep(c("A","B","C"), 10))table(b)table(b, exclude = "B")d <- factor(rep(c("A","B","C"), 10), levels = c("A","B","C","D","E"))table(d, exclude = "B")print(table(b, d), zero.print = ".")## NA counting:is.na(d) <- 3:4d. <- addNA(d)d.[1:7]table(d.) # ", exclude = NULL" is not needed## i.e., if you want to count the NA's of 'd', usetable(d, useNA = "ifany")## "pathological" case:d.patho <- addNA(c(1,NA,1:2,1:3))[-7]; is.na(d.patho) <- 3:4d.patho## just 3 consecutive NA's ? --- well, have *two* kinds of NAs here :as.integer(d.patho) # 1 4 NA NA 1 2#### In R >= 3.4.0, table() allows to differentiate:table(d.patho) # counts the "unusual" NAtable(d.patho, useNA = "ifany") # counts all threetable(d.patho, exclude = NULL) # (ditto)table(d.patho, exclude = NA) # counts none## Two-way tables with NA counts. The 3rd variant is absurd, but shows## something that cannot be done using exclude or useNA.with(airquality, table(OzHi = Ozone > 80, Month, useNA = "ifany"))with(airquality, table(OzHi = Ozone > 80, Month, useNA = "always"))with(airquality, table(OzHi = Ozone > 80, addNA(Month)))# }
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