learning R

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.

a=c(1,2)
names(a)=c("one","two")
names(a[2])
names(a)[2]<-"too"
names(a)

x=c(1,2,3)
y=c(3,4,5)

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

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