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Wiener, Matthew Charles

2001-Oct-30 13:40 UTC

[R] moving dimnames when reassigning

Hi, all.

I've got a question that arose when I was switching some row and columns in
a matrix.  I was expecting the row and column names to follow their rows and
columns, and they didn't.  I think I see some logic to the behavior, but
I'm
not sure whether it's intentional or not, so I thought I'd ask the list
whether this is a feature or a bug.

Here's an example (R-1.3.1, same behavior under Windows NT and Linux).  This
example uses a matrix, and switches columns.  The same thing happens when
using data frames and when switching rows.

> t1 <- matrix(runif(25), 5, 5)
> dimnames(t1) <- list(letters[1:5], LETTERS[1:5])
> t1          A         B                C         	D          E
a 0.8857528 0.1435165 0.44589190 0.1837626 0.000864055
b 0.1867816 0.8102641 0.97127777 0.8952994 0.151531510
c 0.1102591 0.4704422 0.04712121 0.2345568 0.535079125
d 0.7435725 0.7270509 0.49541471 0.3195482 0.892261212
e 0.7610705 0.6057041 0.73183485 0.9959111 0.176386124> 
> t1[,c(1,2)] <- t1[,c(2,1)]
> t1          A         B                C                  D           E
a 0.1435165 0.8857528 0.44589190 0.1837626 0.000864055
The columns switched,
b 0.8102641 0.1867816 0.97127777 0.8952994 0.151531510		but the
column names
c 0.4704422 0.1102591 0.04712121 0.2345568 0.535079125		didn't.
d 0.7270509 0.7435725 0.49541471 0.3195482 0.892261212
e 0.6057041 0.7610705 0.73183485 0.9959111 0.176386124> 
> t1 <- t1[,c(2,1,3,4,5)]
> 
> t1          B         A                C                  D            E
a 0.8857528 0.1435165 0.44589190 0.1837626 0.000864055		The columns
and
b 0.1867816 0.8102641 0.97127777 0.8952994 0.151531510		column names
both
c 0.1102591 0.4704422 0.04712121 0.2345568 0.535079125		switched.
d 0.7435725 0.7270509 0.49541471 0.3195482 0.892261212
e 0.7610705 0.6057041 0.73183485 0.9959111 0.176386124> 

I was rearranging a matrix in the first way, and then found that the row and
column names hadn't followed along.  Two workarounds are to permute the row
and column names separately (which is what I'm doing), or to construct
indices to do things the second way.

If this was a design decision, I'd like to understand the reason for it
better.  If it's unintended, I'll turn this into a bug report.

Regards,

Matt Wiener


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Pierre Kleiber

2001-Oct-30 20:17 UTC

head link

[R] moving dimnames when reassigning

It's not a bug IMHO.  If you want to switch columns as you indicated,
try this:
   > t1 <- t1[,c(2,1,3:5)]
    or
   > t1 <-
t1[,c("B","A","C","D","E")]

The approach for rows would be similar.

Cheers, Pierre


"Wiener, Matthew Charles" wrote:> 
> Hi, all.
> 
> I've got a question that arose when I was switching some row and
columns in
> a matrix.  I was expecting the row and column names to follow their rows
and
> columns, and they didn't.  I think I see some logic to the behavior,
but I'm
> not sure whether it's intentional or not, so I thought I'd ask the
list
> whether this is a feature or a bug.
> 
> Here's an example (R-1.3.1, same behavior under Windows NT and Linux). 
This
> example uses a matrix, and switches columns.  The same thing happens when
> using data frames and when switching rows.
> 
> > t1 <- matrix(runif(25), 5, 5)
> > dimnames(t1) <- list(letters[1:5], LETTERS[1:5])
> > t1
>           A         B                C          D          E
> a 0.8857528 0.1435165 0.44589190 0.1837626 0.000864055
> b 0.1867816 0.8102641 0.97127777 0.8952994 0.151531510
> c 0.1102591 0.4704422 0.04712121 0.2345568 0.535079125
> d 0.7435725 0.7270509 0.49541471 0.3195482 0.892261212
> e 0.7610705 0.6057041 0.73183485 0.9959111 0.176386124
> >
> > t1[,c(1,2)] <- t1[,c(2,1)]
> > t1
>           A         B                C                  D           E
> a 0.1435165 0.8857528 0.44589190 0.1837626 0.000864055
> The columns switched,
> b 0.8102641 0.1867816 0.97127777 0.8952994 0.151531510          but the
> column names
> c 0.4704422 0.1102591 0.04712121 0.2345568 0.535079125          didn't.
> d 0.7270509 0.7435725 0.49541471 0.3195482 0.892261212
> e 0.6057041 0.7610705 0.73183485 0.9959111 0.176386124
> >
> > t1 <- t1[,c(2,1,3,4,5)]
> >
> > t1
>           B         A                C                  D            E
> a 0.8857528 0.1435165 0.44589190 0.1837626 0.000864055          The columns
> and
> b 0.1867816 0.8102641 0.97127777 0.8952994 0.151531510          column
names
> both
> c 0.1102591 0.4704422 0.04712121 0.2345568 0.535079125          switched.
> d 0.7435725 0.7270509 0.49541471 0.3195482 0.892261212
> e 0.7610705 0.6057041 0.73183485 0.9959111 0.176386124
> >
> 
> I was rearranging a matrix in the first way, and then found that the row
and
> column names hadn't followed along.  Two workarounds are to permute the
row
> and column names separately (which is what I'm doing), or to construct
> indices to do things the second way.
> 
> If this was a design decision, I'd like to understand the reason for it
> better.  If it's unintended, I'll turn this into a bug report.
> 
> Regards,
> 
> Matt Wiener
> 
>
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> r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
> Send "info", "help", or "[un]subscribe"
> (in the "body", not the subject !)  To: r-help-request at
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>
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-- 
-----------------------------------------------------------------
Pierre Kleiber             Email: pkleiber at honlab.nmfs.hawaii.edu
Fishery Biologist                     Tel: 808 983-5399/737-7544
NOAA FISHERIES - Honolulu Laboratory         Fax: 808 983-2902
2570 Dole St., Honolulu, HI 96822-2396 
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  all.  But behold... It was good enough for government work."
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Bill.Venables@CMIS.CSIRO.AU

2001-Oct-31 05:11 UTC

head link

[R] moving dimnames when reassigning

This is an instructive example in a minor sort of way; it often clears
things up quite a bit once this lesson is learnt.

An assignment of the form
> name <- value
assigns the name to the value.  An assignment of the form
> name[] <- value
(effectively) uses value to replace the contents of the structure *but keeps
the attributes of name intact*.  By analogy (or extension, whatever),
> t1[, c(1,2)] <- anything.at.all
will simply take the atomic part of anything.at.all and use it to replace
the contents of the first and second columns of the matrix structure t1, but
leaving all attributes (such as dimnames) intact.

This is not a bug but a feature.  There are times when you want to do this
and this is about the only elegant way for doing it.

Bill Venables, 
CMIS, CSIRO Marine Laboratories, 
PO Box 120, Cleveland, Qld. 4163
AUSTRALIA
Phone:  +61 7 3826 7251  
Fax:    +61 7 3826 7304
Mobile: +61 419 634 642
<mailto: Bill.Venables at csiro.au>
http://www.cmis.csiro.au/bill.venables/

>  -----Original Message-----
> From: 	Wiener, Matthew Charles [mailto:matthew_wiener at merck.com] 
> Sent:	Tuesday, 30 October 2001 11:40 PM
> To:	R-help
> Subject:	[R] moving dimnames when reassigning
> 
> Hi, all.
> 
> I've got a question that arose when I was switching some row and
columns
in> a matrix.  I was expecting the row and column names to follow their rows
and> columns, and they didn't.  I think I see some logic to the behavior,
but
I'm> not sure whether it's intentional or not, so I thought I'd ask the
list
> whether this is a feature or a bug.
> 
> Here's an example (R-1.3.1, same behavior under Windows NT and Linux).
This> example uses a matrix, and switches columns.  The same thing happens when
> using data frames and when switching rows.
> 
> 
> > t1 <- matrix(runif(25), 5, 5)
> > dimnames(t1) <- list(letters[1:5], LETTERS[1:5])
> > t1
>           A         B                C         	D          E
> a 0.8857528 0.1435165 0.44589190 0.1837626 0.000864055
> b 0.1867816 0.8102641 0.97127777 0.8952994 0.151531510
> c 0.1102591 0.4704422 0.04712121 0.2345568 0.535079125
> d 0.7435725 0.7270509 0.49541471 0.3195482 0.892261212
> e 0.7610705 0.6057041 0.73183485 0.9959111 0.176386124
> > 
> > t1[,c(1,2)] <- t1[,c(2,1)]
> > t1
>           A         B                C                  D           E
> a 0.1435165 0.8857528 0.44589190 0.1837626 0.000864055
> The columns switched,
> b 0.8102641 0.1867816 0.97127777 0.8952994 0.151531510		but
the> column names
> c 0.4704422 0.1102591 0.04712121 0.2345568 0.535079125
didn't.> d 0.7270509 0.7435725 0.49541471 0.3195482 0.892261212
> e 0.6057041 0.7610705 0.73183485 0.9959111 0.176386124
> > 
> > t1 <- t1[,c(2,1,3,4,5)]
> > 
> > t1
>           B         A                C                  D            E
> a 0.8857528 0.1435165 0.44589190 0.1837626 0.000864055		The
columns> and
> b 0.1867816 0.8102641 0.97127777 0.8952994 0.151531510
column names> both
> c 0.1102591 0.4704422 0.04712121 0.2345568 0.535079125
switched.> d 0.7435725 0.7270509 0.49541471 0.3195482 0.892261212
> e 0.7610705 0.6057041 0.73183485 0.9959111 0.176386124
> > 
> 
> 
> I was rearranging a matrix in the first way, and then found that the row
and> column names hadn't followed along.  Two workarounds are to permute the
row> and column names separately (which is what I'm doing), or to construct
> indices to do things the second way.
> 
> If this was a design decision, I'd like to understand the reason for it
> better.  If it's unintended, I'll turn this into a bug report.
> 
> Regards,
> 
> Matt Wiener
> 
> 
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http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html> Send "info", "help", or "[un]subscribe"
> (in the "body", not the subject !)  To: r-help-request at
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R help - Oct 2001 - moving dimnames when reassigning

[R] moving dimnames when reassigning

[R] moving dimnames when reassigning

[R] moving dimnames when reassigning