如何在R中的data.table对象列中找到每个类别的计数？
要查找data.tableR中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，与n一起分组后使用dplyr包的汇总功能。
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输出结果执行时，上述脚本生成以下内容output(thisoutputwillvaryonyoursystemduetorandomization)-
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
在与n一起分组后使用dplyr包的汇总函数来查找data.table对象DT的因子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())输出结果# 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