Why can't this function be used with the 'by' command?
I believe it has to do with passing multiple columns to the shapiro.test. Note that by(x[,1:2], x$group, function(x) shapiro.test(x)[[2]]) doesn't work but by(x[,1:2], x$group, function(x) shapiro.test(x[,1])[[2]]) does. Michael
On Thu, Nov 3, 2011 at 8:08 AM, Kaiyin Zhong <kindlychung at gmail.com> wrote:
Why can't this function be used with the 'by' command?
x = array(runif(16), dim=c(8,2))
x = data.frame(x)
x$group = rep(c('wt', 'app'), each=4)
shapiro.p = function(x) shapiro.test(x)[[2]] apply(x[,1:2], 2, shapiro.p)
? ? ? X1 ? ? ? ?X2 0.4126345 0.2208781
by(x[,1:2], x$group, shapiro.p)
Error in `[.data.frame`(x, complete.cases(x)) : ?undefined columns selected ? ? ? ?[[alternative HTML version deleted]]
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