Mapreduce in R - how can i implement "loop if" in reduce? -

this illustration dataset:

x <- c("a1", "a1", "a1", "a2", "a2", "a2", "a2", "a3") y <- c(5347, 5347, 5347, 1819, 1758, 1212, 1212, 1456)

i can't prepare dataset input mapreduce's query after "map|sort", because have separate \t , after (it's necessary step in mapreduce split rows):

fields <- unlist(strsplit(line, "\t"))

where line input 2 fields:

fields[[1]] = all column x fields[[2]] = all column y

i want result:

id count unique number a1 1 (only 5347) a2 3 (1819, 1758, 1212) a3 1 (only 1456)

how can count this, loop observe column x , y long search new number in column x , count unique number in column y unique number in column x??

the question not clear (maybe because of english language problem). expected result, think looking like:

tapply(y,x,function(t)length(unique(t))) a1 a2 a3 1 3 1

which in english language :

computing number of unique y each x.

r loops if-statement mapreduce

Three