[R] Explanation w.r.t. rbind, please!

[Meyners, Michael, LAUSANNE, AppliedMathematics]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Uwe Dippel
> Sent: Freitag, 29. Januar 2010 11:57
> To: r-help at r-project.org
> Subject: [R] Explanation w.r.t. rbind, please!
> 
> This is what I tried:
> 
>  > num.vec <- c(12.34,56.78,90.12,34.56)  > 
> names(num.vec)<-c("first","second","third","fourth")
>  > num.vec
>  first second  third fourth
>  12.34  56.78  90.12  34.56
>  > seq<-(1:4)                          
>  > num.mat<-rbind(num.vec,seq)
>  > num.mat                   
>         first second third fourth
> num.vec 12.34  56.78 90.12  34.56
> seq      1.00   2.00  3.00   4.00
>  > num.vec [3:4]
>  third fourth
>  90.12  34.56
> 
> (until here I'm fine)
> 
>  > num.mat [seq]
> [1] 12.34  1.00 56.78  2.00

What you (probably) want here is
num.mat ["seq",]

>  > num.mat [num.vec]
> [1] NA NA NA NA   

num.mat["num.vec",]

and so on. You have to use tell R that you want the ROW (that's why the
comma is needed) defined by the NAME "seq" or "num.vec" (that's why you
need "") . Otherwise, R replaces seq by its value 1:4, so 
num.mat[seq] 
is identical to 
num.mat[1:4] 
(and num.mat[12.34] is NA of course in num.mat[num.vec])

You should have a closer look at ?Extract
HTH, Michael

>  > num.vec [seq]
>  first second  third fourth
>  12.34  56.78  90.12  34.56
>  > num.mat [num.vec]        
> [1] NA NA NA NA            
>  > num.mat [-seq]          
> [1] 90.12  3.00 34.56  4.00
> 
> (and here I'm lost!)
> 
> How could I display a row, instead of always seemingly 
> falling back to columns?
> 
> Uwe
> 
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