I am trying to compare a series of rows and a fixed vector in R and flag them as identical (TRUE) or not identical (FALSE). Imagine the problem as comparing a set of test responses to an answer key.
I have been able to get the comparison to work using a loop and the COMPARE package, but I have been unable to duplicate it using more efficient methods such as BY, APPLY or DDPLY:
test.answers <- as.data.frame(rbind(c(ID="A",rep(3, 6)), c(ID="B",6:1), c(ID="C",1:6)))
library(compare)
# Compare using a loop
for (i in 1:length(test.answers))
{
test.answers$Static1[i] <- isTRUE(compare(as.data.frame(rbind(rep(3, 6))),
test.answers[i,2:7], allowAll=TRUE))
}
test.answers # This is correct!
staticfn <- function(x)
{
isTRUE(compare(as.data.frame(rbind(rep(3, 6))),
test.answers[2:7], allowAll=TRUE))
}
# Compare using APPLY
test.answers$Static2 <- apply(test.answers, 1, staticfn)
test.answers # This is incorrect!
# Compare using BY
test.answers$Static3 <- by(test.answers, test.answers$ID, staticfn)
test.answers # This is incorrect!
# Compare using DDPLY
library(plyr)
test.answers <- ddply(test.answers, .(ID), { staticfn })
test.answers # This is incorrect!
# Results
ID V2 V3 V4 V5 V6 V7 Static1 Static2 Static3
1 A 3 3 3 3 3 3 TRUE TRUE TRUE
2 B 6 5 4 3 2 1 FALSE TRUE TRUE
3 C 1 2 3 4 5 6 FALSE TRUE TRUE
ID V1
1 A TRUE
2 B TRUE
3 C TRUE
I'd be grateful if someone could suggest why APPLY and DDPLY are giving me a different result than the loop, and how I could modify one of these functions to avoid using a loop.
You're making this much too complicated:
apply(test.answers,1,function(x){all(x[-1] == rep(3,6))})
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