How to select rows by group with the minimum value and containing NAs in R

Question

Here is an example:

set.seed(123)    
data<-data.frame(X=rep(letters[1:3], each=4),Y=sample(1:12,12),Z=sample(1:100, 12))
data[data==3]<-NA
         


        

Answer 1

Using the data.table package, this is trivial:

library(data.table)

d <- data.table(data)
d[, min(Y, na.rm=TRUE), by=X]

You can also use plyr and its ddply function:

library(plyr)

ddply(data, .(X), summarise, min(Y, na.rm=TRUE))

Or using base R:

aggregate(X ~ ., data=data, FUN=min)

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Based on the edits, I would use data.table for sure:

d[, .SD[which.min(Y)], by=X]

However, there are solutions using base R or other packages.