Hi,
## Better way to make your matrix
A <- rbind(c(16,10,2,4,8,7),
c(16,10,12,14,8,7),
c(16,10,13,15,19,17),
c(16,9,13,15,9,7))
## Create logical matrices for conditions 1 & 2
B1 <- rowSums(A[, 2:4] < 10) > 0
B2 <- rowSums(A[, 5:6] < 10) > 0
## initialize X at the "catch all"
X <- rep(3L, nrow(A))
## overwrite values of X that meet condition 2
X[B2] <- 2L
## overwrite values of X that meet condition 1
X[B1] <- 1L
## Now turn these steps into a little function
## for benchmarking
make.ind <- function(A) {
B1 <- rowSums(A[, 2:4] < 10) > 0
B2 <- rowSums(A[, 5:6] < 10) > 0
X <- rep(3L, nrow(A))
X[B2] <- 2L
X[B1] <- 1L
return(X)
}
## replicate A to have 4 million rows
Abig <- do.call("rbind", rep(list(A), 10^6))
system.time(Xbig <- make.ind(Abig))
## On my system it takes less than 1 second
# user system elapsed
# 0.72 0.00 0.72
Hope this helps,
Josh
On Sun, Aug 7, 2011 at 10:50 PM, gallon li <gallon...@gmail.com> wrote:
> Suppose I have a matrix like
>
> A=matrix(0,4,6)
> A[1,]=c(16,10,2,4,8,7)
> A[2,]=c(16,10,12,14,8,7)
> A[3,]=c(16,10,13,15,19,17)
> A[4,]=c(16,9,13,15,9,7)
>
>> A
> [,1] [,2] [,3] [,4] [,5] [,6]
> [1,] 16 10 2 4 8 7
> [2,] 16 10 12 14 8 7
> [3,] 16 10 13 15 19 17
> [4,] 16 9 13 15 9 7
> I want to creat an indicator variable X which takes three values:
>
> X=1 if any of A[,2] to A[,4] is less than 10; for example, A[1,] and A[4,]
> is this group;
> X=2 if not the above but any of A[,5] to A[,6] is less than 10; for example,
> A[2,] is this group;
> X=3 if none of the above; for example, A[3,] belongs here.
>
> I wonder how to implement this fast in R?
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
--
Joshua Wiley
Ph.D. Student, Health Psychology
Programmer Analyst II, ATS Statistical Consulting Group
University of California, Los Angeles
https://joshuawiley.com/
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