Hi,

I'm working with R and I have a code like this:

i<-1
j<-1
for (i in 1:10)
   for (j in 1:100)
        if (data[i] == paths[j,1])
            cluster[i,4] <- paths[j,2]

where :

• data is a vector with 100 rows and 1 column
• paths is a matrix with 100 rows and 5 columns
• cluster is a matrix with 100 rows and 5 columns

My question is: how could I avoid the use of "for" loops to iterate through the matrix? I don't know whether apply functions (lapply, tapply...) are useful in this case.

This is a problem when j=10000 for example, because execution time is very long.

Thank you