temps[temps$country != "mycountry",]

基准

set.seed(24)
temps1 <- data.frame(country = sample(LETTERS,1e7,replace=TRUE),val = rnorm(1e7))
system.time(temps1[!temps1$country %in% "A",])
#  user  system elapsed 
#   0.92    0.11    1.04 
system.time(temps1[temps1$country != "A",])
#   user  system elapsed 
#   0.70    0.17    0.88

如果我们使用包解决方案

library(sqldf)
system.time(sqldf("SELECT * FROM temps1 WHERE country != 'A'"))
#   user  system elapsed 
# 12.78    0.37   13.15 
 
library(data.table)
system.time(setDT(temps1,key = 'country')[!("A")])
#   user  system elapsed 
#  0.62    0.19    0.37