Hi Jack,
Maybe this helps.
# make some data
set.seed(123)
condition <- factor(rep(c("a","b"), each = 5))
score <- rnorm(10);
lg <- data.frame(condition, score)
# Carry out commands
a <- subset(lg,condition=="a")["score"]
b <- subset(lg,condition=="b")["score"]
t.test(a,b,paired=TRUE)
#Error in `[.data.frame`(y, yok) : undefined columns selected
# a and b are still data frames
#So this works. We must refer to score, which is being compared.
t.test(a$score,b$score,paired=TRUE)
a=a[,1]
b=b[,1]
# This now works because a and b are vectors
# so we don't need $ to access score
t.test(a,b, paired=TRUE)
Regards,
Juliet
______________________________________________
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.
