[R] learning R

markleeds at verizon.net markleeds at verizon.net
Wed Feb 25 06:18:04 CET 2009

Hi Ira:

For your first question, under the hood of R, names<- is actually a 
function so , when you do that, you need to say names(a)[2] rather
than names(a[2]). why this is is tricky and I wouldn't do it justice if 
i tried to explain it. it's best if you do ?"names<-" at an R prompt and 
read that.

For the second one, you can rbind x with anything that of length one and 
the recycling concept in R will add the extra now but maybe there's a 
better way that someone else will hopefully send.





x <- matrix(x,nrow=1)
x <- rbind(x,NA)
x[2,] <- y

On Tue, Feb 24, 2009 at 11:36 PM, Fuchs Ira wrote:

> I was wondering why the following doesn't work:
>> a=c(1,2)
>> names(a)=c("one","two")
>> a
> one two
>   1   2
>> names(a[2])
> [1] "two"
>> names(a[2])="too"
>> names(a)
> [1] "one" "two"
>> a
> one two
>   1   2
> I must not be understanding some basic concept here.
> Why doesn't the 2nd name change to "too"?
> also unrelated:  if I have two vectors and I want to combine them to 
> form a matrix ,is cbind (or rbind) the most direct way to do this?
> e.g.
> x=c(1,2,3)
> y=c(3,4,5)
> z=rbind(x,y)
> alternatively: is there a way to make a matrix with dim=2,3 and then 
> to replace the 2nd row with y
> something like this (which doesn't work but perhaps there is another 
> way to do the equivalent?)
> attr(x,"dim")=c(2,3)
> x[2,]=y
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