coded to categorical variables in a large dataset
As Richard has already pointed out you may only need to convert your
numeric vector to a factor but just in case here are a few direct answers:
Using X from Chuck's post here are two ways of creating a 100x5
matrix of indicator variables:
model.matrix(~ X-1, list(X = factor(X)))
outer(X, 1:5, "==")+0
# To create eventi variables
# here is a way of creating them
event1 <- (X == 1) + 0 # and similarly for 2, 3, 4, 5
# or do it in a loop
for(i in 1:5) assign(paste("event", i, sep = ""), (X == i) + 0)
# or create as columns of a data frame
f <- function(i, j) (X == j) + 0
as.data.frame(mapply(f, paste("event", 1:5, sep = ""), 1:5))
On 12/29/06, sj <ssj1364 at gmail.com> wrote:
I am working with a dataset where there are 5 possible outcomes (coded 1:5),
I would like to create 5 categorical variables (event1...event5). I am using
a for loop an if statements, but I have a large dataset( approx 100,000
rows) it takes quite a bit of time, is there a way to speed this up? Here is
some sample code of what I am currently doing.
test2 <-rep(seq(1:5),2000)
event1 <- rep(0,nrow(test2))
event2 <- rep(0,nrow(test2))
event3 <- rep(0,nrow(test2))
event4 <- rep(0,nrow(test2))
event5 <- rep(0,nrow(test2))
for(i in 1:length(event1))
{
if (test2[i]==1)
{
event1[i]=1
}
if (test2[i]==2)
{
event2[i]=1
}
if (test2[i]==3)
{
event3[i]=1
}
if (test2[i]==4)
{
event4[i]=1
}
if (test2[i]==5)
{
event5[i]=1
}
}
thanks,
Spencer
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