dplyr,r：一次在多列中计算特定值[重复]

Question

我有一个数据帧：

md <- data.frame(a = c(3,5,4,5,3,5), b = c(5,5,5,4,4,1), c = c(1,3,4,3,5,5),
      device = c(1,1,2,2,3,3))
myvars = c("a", "b", "c")
md[2,3] <- NA
md[4,1] <- NA
md

library(dplyr)
group_by(md, device) %>% 
summarise(counts.a = sum(a==5, na.rm = T),
          counts.b = sum(b==5, na.rm = T),
          counts.c = sum(c==5, na.rm = T))

谢谢！

Answer 1

如果你关心以“counts”开头的名字。你可以在dplyr管道中这样做：

md %>% 
  group_by(device) %>% 
  summarise_each_(funs(sum(.==5,na.rm=TRUE)), myvars) %>% 
  setNames(c(names(.)[1], paste0("counts.", myvars)))
#Source: local data frame [3 x 4]
#
#  device counts.a counts.b counts.c
#1      1        1        2        0
#2      2        0        1        0
#3      3        1        0        2

这里还有另一个关于如何命名DPLYR的mutate_each生成的新列（其行为与summarise_each)相同）的问答：dplyr中的mutate_each：如何选择某些列并为变异列命名？。