Thanks Arun and Jim; this helps me sort out several points I hadn't been
aware of!   -David


On Sat, Feb 15, 2014 at 1:39 PM, arun <smartpink111@yahoo.com> wrote:

>
>
> Hi David,
> Try:
> Check the output of:
> lapply(mm,function(x) x) #mm is matrix
> #and
> lapply(as.data.frame(mm),function(x) x)
>
>
>
>
>   sapply(split(mm,col(mm)),function(x){out <-
> t.test(x[1:15],x[16:25])$p.value})
>  #       1         2
> #0.1091573 1.0000000
>
>
> #or
>  sapply(as.data.frame(mm), function(x)  t.test(x[1:15],x[16:25])$p.value)
> #       V1        V2
> #0.1091573 1.0000000
>
> A.K.
>
>
> On Saturday, February 15, 2014 3:19 PM, David Romano <dromano@stanford.edu>
> wrote:
> Hi folks,
>
> I'm having trouble with code that used to work, and I can't figure out
> what's going wrong.  I'd be grateful for any help in sorting this out.
>
>
> Suppose I define a matrix
> > mm <- matrix(1:15, 25,2)
> and compare the first 15 values of column 1 of mm to the values remaining
> in the same column and obtain p values as follows:
> > c1 <- mm[,1]
> > out <- t.test(c1[1:15],c1[16:25]) ; out$p.value
>
> This of course works fine, but if I try to embed this line in a call to
> sapply to repeat this for each column, I get the following:
> > mm.pvals <- sapply(mm, function(x) {out <- t.test(x[1:15],x[16:25]) ;
> out$p.value})
> Error in t.test.default(x[1:15], x[16:25]) : not enough 'x' observations
>
> What is baffling is code like this has worked for me before, and I can't
> tell what's triggering the error.
>
> Thanks in advance for your help!
>
> Best,
> David
>
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>
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>
>
> ______________________________________________
> R-help@r-project.org mailing list
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>

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