【描述】
tableuses the cross-classifying factors to build a contingency table of the counts at each combination of factor levels.
table使用交叉分类因子来建立每个因子水平组合的计数列联表。
【用法】
1、统计元素次数
2、结果提取
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 class 'table'
as.data.frame(x, row.names = NULL, ...,
responseName = "Freq", stringsAsFactors = TRUE,
sep = "", base = list(LETTERS))
【参数】
...
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” arrays.
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.
【代码】
> test <- c(1,2,3,2,1,1,5,6,4,5,1)
> table(test)
1 2 3 4 5 6 #test中的元素
4 2 1 1 2 1 #各个元素出现的频率
> test <- sample(c("a", "b", "c"), 100, replace=TRUE)
> names(table(test))
[1] "a" "b" "c"
> as.numeric(table(test))
[1] 42 25 33
> as.data.frame(table(test))
x Freq
1 a 42
2 b 25
3 c 33
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