如何在 R 中查找 data.table 对象列中每个类别的计数?
r programmingserver side programmingprogramming更新于 2025/4/8 0:07:17
要在 R 中查找 data.table 对象列中每个类别的计数，我们可以按照以下步骤操作 −
首先，创建一个 data.table 对象。
然后，在与 n 一起分组后使用 dplyr 包的 summarise 函数。
示例
创建 data.table 对象
让我们创建一个 data.table 对象，如下所示 −
library(data.table)
factor<-sample(c("very low","low","medium","high","very high"),25,replace=TRUE)
response<-rnorm(25)
DT<-data.table(factor,response)
DT
输出
执行时，上述脚本会生成以下输出(由于随机化，此输出将因您的系统而异) −
factor response 1: very high -0.14064701 2: high -0.36029663 3: low -0.50825291 4: very high -2.07959316 5: high 0.25578922 6: very high 1.17946264 7: low 1.32803179 8: medium -0.23736325 9: medium -0.07440274 10: very low 0.32669673 11: very low 0.54953485 12: high -0.93197732 13: very high -0.77787846 14: very low 0.63808636 15: very high 0.76008767 16: very high -0.38712279 17: very high -0.64259955 18: high 0.30249791 19: high 0.16984229 20: very low -0.24732679 21: high -0.47456705 22: low 0.08789350 23: low 0.32541943 24: medium -0.27170782 25: high -0.09860207 factor response
查找 data.table 对象中每个类别的计数
使用 dplyr 包的 summarise 函数，在对 n 进行分组后，查找 data.table 对象 DT 的 factor 列中每个类别的计数−
library(data.table)
factor<-sample(c("very low","low","medium","high","very high"),25,replace=TRUE)
response<-rnorm(25)
DT<-data.table(factor,response)
library(dplyr)
DT %>% group_by(factor) %>% summarise(count=n())
输出
# A tibble: 5 x 2 factor count <chr> <int> 1 high 7 2 low 4 3 medium 3 4 very high 7 5 very low 4
