On 2012-07-03 17:23, jin...@ga.gov.au wrote:
Thank you all for providing various alternatives. They are all pretty fast.
Great help! Based on a test of a dataset with 800,000 rows, the time used
varies from 0.04 to 11.56 s. The champion is:
a1$h2 <- 0
a1$h2[a1$h1=="H"] <- 1
Interesting. My testing shows that Petr's solution is about
twice as fast. Not that it matters much - the time is pretty
small in any case.
a0 <- data.frame(h1 = sample(c("H","J","K"), 1e7, replace = TRUE),
stringsAsFactors = FALSE)
a1 <- a0
system.time({a1$h2 <- 0; a1$h2[a1$h1 == "H"] <- 1})
# user system elapsed
# 1.47 0.48 1.96
a11 <- a1
a1 <- a0
system.time(a1$h2 <- (a1$h1 == "H") * 1)
# user system elapsed
# 0.37 0.17 0.56
a12 <- a1
all.equal(a11,a12)
#[1] TRUE
Peter Ehlers
Regards,
Jin
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