Remove records from a large dataframe

Hi, I am trying to remove a series of records from a large dataframe. The
script I have written works fine but takes a long time to run. Can anyone
suggest a quicker way to do this?

Here is an example of the code I've written. The end result of this bit of
code would be a dataframe with any records relating to ID 1 or ID 4 removed:

#dataframe
id <-     c(1,1,1,1,2,2,2,2,2, 3,3,3, 4,4)
year <- c(1,1,1,2, 2,2,3,2,2, 2,3,4, 8,8)
age <-  c("Adult",NA,NA,NA, "Adult",NA,NA,NA, "Adult",
          NA,"Adult",NA, NA,"Adult")
dat <- data.frame(id, year, age)
dat.id<-unique(dat$id)

#ID numbers for removal
bad<- data.frame(c(1,4))
names(bad)<-"id"
remove.value<-bad$id


good.id<- dat.id[!dat.id%in%remove.value]

#Combine all good ID numbers
if(exists("dat.2")){ rm(dat.2)}

for(i in good.id){
     lala<-dat[which(dat$id==i),]

      if(!exists("dat.2")) {
       dat.2 <- lala } else {
       dat.2 <- rbind(dat.2, lala)
       }
}

Many thanks in advance for any suggestions



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