R help - Jun 2006 - Strange behaviour of cbind

Hi,

Is this intended behaviour of cbind?
> a<-c(0,1,2,3)
> a
[1] 0 1 2 3
> a<-as.ordered(a)
> a
[1] 0 1 2 3
Levels: 0 < 1 < 2 < 3
> a<-a[a!=0] #remove the zero from a
> a
[1] 1 2 3
Levels: 0 < 1 < 2 < 3
> cbind(a) 
     a
[1,] 2
[2,] 3
[3,] 4

#cbind adds +1 to each element
> a<-as.ordered(as.vector(a))
> a
[1] 1 2 3
Levels: 1 < 2 < 3
> cbind(a)
     a
[1,] 1
[2,] 2
[3,] 3

#now it works...

I am running R 2.3.0 on a windows system.



Regards,

Dirk Vandekerckhove

On Tue, 2006-06-06 at 13:44 -0700, Dirk Vandekerckhove
wrote:
> Hi,
> 
> Is this intended behaviour of cbind?
> 
> > a<-c(0,1,2,3)
> > a
> [1] 0 1 2 3
> > a<-as.ordered(a)
> > a
> [1] 0 1 2 3
> Levels: 0 < 1 < 2 < 3
> > a<-a[a!=0] #remove the zero from a
> > a
> [1] 1 2 3
> Levels: 0 < 1 < 2 < 3
> > cbind(a) 
>      a
> [1,] 2
> [2,] 3
> [3,] 4
> 
> #cbind adds +1 to each element
Does this help?
> a
[1] 1 2 3
Levels: 0 < 1 < 2 < 3
> as.integer(a)
[1] 2 3 4

Note in ?cbind, the Details section indicates:

"In the default method, all the vectors/matrices must be atomic (see
vector) or lists (e.g., not expressions)."

For a factor, the atomic data type is the underlying integer vector.
You eliminated '0' from the original ordered factor, which had an
integer value of 1 (not 0!):
> a
[1] 0 1 2 3
Levels: 0 < 1 < 2 < 3
> as.integer(a)
[1] 1 2 3 4

Unless you re-level the factor (as you do below) the other elements
retain the original integer values.
> > a<-as.ordered(as.vector(a))
> > a
> [1] 1 2 3
> Levels: 1 < 2 < 3
> > cbind(a)
>      a
> [1,] 1
> [2,] 2
> [3,] 3
> 
> #now it works...
Yep, you re-leveled 'a', so the integer values now correspond to the
levels:
> a<-as.ordered(as.vector(a))
> a
[1] 1 2 3
Levels: 1 < 2 < 3
> as.integer(a)
[1] 1 2 3


HTH,

Marc Schwartz

Hi,

It doesn't have anything to with cbind, but rather with
as.ordered - you converted it to a factor in that step.

In the cbind step, you are actually getting the position of
that ordered factor, rather than anything to do with the values
themselves.
> a <- c(1,7,5,3)
> a <- as.ordered(a)
> a
[1] 1 7 5 3
Levels: 1 < 3 < 5 < 7
> cbind(a)
     a
[1,] 1
[2,] 4
[3,] 3
[4,] 2

The original values could be letters, or anything, and you'd
still get the same result with the same ordering.

Sarah


On 6/6/06, Dirk Vandekerckhove <dvdkerc@yahoo.com>
wrote:
>
> Hi,
>
> Is this intended behaviour of cbind?
>
> > a<-c(0,1,2,3)
> > a
> [1] 0 1 2 3
> > a<-as.ordered(a)
> > a
> [1] 0 1 2 3
> Levels: 0 < 1 < 2 < 3
> > a<-a[a!=0] #remove the zero from a
> > a
> [1] 1 2 3
> Levels: 0 < 1 < 2 < 3
> > cbind(a)
>      a
> [1,] 2
> [2,] 3
> [3,] 4
>
> #cbind adds +1 to each element
>
> > a<-as.ordered(as.vector(a))
> > a
> [1] 1 2 3
> Levels: 1 < 2 < 3
> > cbind(a)
>      a
> [1,] 1
> [2,] 2
> [3,] 3
>
> #now it works...
>
> I am running R 2.3.0 on a windows system.
>
>
>
> Regards,
>
> Dirk Vandekerckhove
>
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>


-- 
Sarah Goslee

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