[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.
#==================================================================================
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
>
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