[R] Replace values on seq

Walter Alini
Tue, 23 Oct 2007 20:17:32 -0000

Hey guys, sorry for the inconvenience (this might be a hundred times
answered question), but I have been searching a while and gave up
about the following:

I have the following, table and data:

table <- seq(255, 0, by=-1)
data  <- c(1,8,...)   <--- doesn't matter what's in here

Which would be the most efficient way to replace each data value, v_i,
by table[v_i + 1] ?
And, maybe more important, why is that more efficient?

I used this, but I think is not the best option:

for (i in 1:length(data)){
	data[i] <- table[data[i]+1]
}

Then used mapply, that seems to work better:

f<-function(x){
   255-x
}

mapply(f, data)

Thanks guys in advance,
Walter