R help - Jul 2009 - strange dlply behavior

I'm running R 2.9.1 on winXP, using the library plyr.

Can anyone explain to me what is going wrong in this code? (in particular
see lines marked with ******************) Trying to modify objects in a list
created using dlply seems to corrupt the objects in the list.
> library(plyr)
> d=as.data.frame(cbind(c(1,1,1,2,2,2),c(1,2,3,4,5,6)))
> d
  V1 V2
1  1  1
2  1  2
3  1  3
4  2  4
5  2  5
6  2  6
> c=dlply(d,.(V1))
> c
[[1]]
  V1 V2
1  1  1
2  1  2
3  1  3

[[2]]
  V1 V2
4  2  4
5  2  5
6  2  6

## display an element from the second data frame
> c[[2]][2,2]
[1] 5

## change element in the second data from
> c[[2]][2,2]=10
> c
[[1]]
    V1 V2
2    1  2    **************
2.1  1  2   **************  What happened to V2?
2.2  1  2   **************

[[2]]
   V1 V2
4   2  4
NA NA NA **********************************
6   2  6

##Try again with first data frame
> c=dlply(d,.(V1))
> c[[1]][2,2]=10 **********************************
> c
[[1]]
NULL ********************************* YIKES!


##Try again but copy c into a new list k
> c=dlply(d,.(V1))
> k=list(c[[1]],c[[2]])
> k[[1]]
  V1 V2
1  1  1
2  1  2
3  1  3
> k[[2]][2,2]=10
> k
[[1]]
  V1 V2
1  1  1
2  1  2
3  1  3

[[2]]
  V1 V2
4  2  4
5  2 10 ***************************
6  2  6
> k[[1]][2,2]=10
> k
[[1]]
  V1 V2
1  1  1
2  1 10 *******************************
3  1  3

[[2]]
  V1 V2
4  2  4
5  2 10
6  2  6

	[[alternative HTML version deleted]]

Hi Damien,

This is because of a small bug.  You can work around it by explicitly
using the force function - dlply(d, "V1", force).  The default will be
fixed in the next version.

Regards,

Hadley

On Tue, Jul 21, 2009 at 11:18 AM, Damien Moore<damienlmoore at gmail.com>
wrote:
> I'm running R 2.9.1 on winXP, using the library plyr.
>
> Can anyone explain to me what is going wrong in this code? (in particular
> see lines marked with ******************) Trying to modify objects in a
list
> created using dlply seems to corrupt the objects in the list.
>
>> library(plyr)
>> d=as.data.frame(cbind(c(1,1,1,2,2,2),c(1,2,3,4,5,6)))
>> d
> ?V1 V2
> 1 ?1 ?1
> 2 ?1 ?2
> 3 ?1 ?3
> 4 ?2 ?4
> 5 ?2 ?5
> 6 ?2 ?6
>> c=dlply(d,.(V1))
>> c
> [[1]]
> ?V1 V2
> 1 ?1 ?1
> 2 ?1 ?2
> 3 ?1 ?3
>
> [[2]]
> ?V1 V2
> 4 ?2 ?4
> 5 ?2 ?5
> 6 ?2 ?6
>
> ## display an element from the second data frame
>> c[[2]][2,2]
> [1] 5
>
> ## change element in the second data from
>> c[[2]][2,2]=10
>> c
> [[1]]
> ? ?V1 V2
> 2 ? ?1 ?2 ? ?**************
> 2.1 ?1 ?2 ? ************** ?What happened to V2?
> 2.2 ?1 ?2 ? **************
>
> [[2]]
> ? V1 V2
> 4 ? 2 ?4
> NA NA NA **********************************
> 6 ? 2 ?6
>
> ##Try again with first data frame
>> c=dlply(d,.(V1))
>> c[[1]][2,2]=10 **********************************
>> c
> [[1]]
> NULL ********************************* YIKES!
>
>
> ##Try again but copy c into a new list k
>> c=dlply(d,.(V1))
>> k=list(c[[1]],c[[2]])
>> k[[1]]
> ?V1 V2
> 1 ?1 ?1
> 2 ?1 ?2
> 3 ?1 ?3
>> k[[2]][2,2]=10
>> k
> [[1]]
> ?V1 V2
> 1 ?1 ?1
> 2 ?1 ?2
> 3 ?1 ?3
>
> [[2]]
> ?V1 V2
> 4 ?2 ?4
> 5 ?2 10 ***************************
> 6 ?2 ?6
>> k[[1]][2,2]=10
>> k
> [[1]]
> ?V1 V2
> 1 ?1 ?1
> 2 ?1 10 *******************************
> 3 ?1 ?3
>
> [[2]]
> ?V1 V2
> 4 ?2 ?4
> 5 ?2 10
> 6 ?2 ?6
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
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>


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