array manipulation simple questions
2009/2/23 ???????? ??????? <bleonidas25 at yahoo.gr>:
Hi there, I am pretty new to R. Actually I started using it yesterday. I have?two questions: 1.?? Suppose I have a<-c(1:10)? (or a<-array(c(1:10),dim=c(1,10))) and I want to end up with vector b=[0 0 0 0 0 1 1 1 1 1]. i.e. I want to substitute alla elements that are <5 with 0 and >5 with 1. I did this by using a for loop. Is there another function to use so as to avoid the "for"?
(a>5)+0 # or out <- as.numeric(a > 5) if (is.matrix(a)) out <- matrix(a, 1) out
2.? Suppose I have a<-c(1,1,2,2,3,3)? (or array again) And I want to place a "4,5" before every "2" and end up with a new "bigger" vector "b": b=[1 1 4 5 2 4 5 2 3 3]
# return c(4, 5, 2) or x f <- function(x) if (x==2) c(4:5, x) else x # apply f to each element and # if a is a matrix make output a matrix too out <- unlist(sapply(a, f)) if (is.matrix(a)) out <- matrix(out, nrow(a)) out
Also I want to find where the 2's in?array "a"?(if it was an array) are located i.e. positions 3,4.
which(a == 2)