R help - Feb 2004 - interesting feature

Hi, everybody.
This was an interesting discussion last time and it helped me a lot.

Could you please have a look at some feature and tell me
why it was designed this way
(my questions are under #########)
> x = c(1, 10)
> y = c(99, 55)
> d <- data.frame(x = x, y = y)
> d
   x  y
1  1 99
2 10 55
> add <- data.frame(x = 14, y = 99)
> add
   x  y
1 14 99
> d <- rbind(d, add)
> d
    x  y
1   1 99
2  10 55
11 14 99
######### it would be more natural to index the rows: 1,2,3 instead of
#1,2,11  ?!
>
> d[3,1]
[1] 14
> d[11,1]
[1] NA
######### especially if index '11' is not
functioning...
>
> add1 <- data.frame(x = 10, y = 87)
> d <- rbind(d, add)
######### now I would think that the next index should be 21,
BUT:
> d
    x  y
1   1 99
2  10 55
11 14 99
12 10 87
######### so what is the intuition of such indexing?


-- 
Svetlana Eden        Biostatistician II            School of Medicine
                     Department of Biostatistics   Vanderbilt University

You are adding a row with name "1" each time.  R just adds a suffix to
make it unique.  What you call indices are the *row names* of the data 
frame.

Suppose the row name had been "Eden".  Then "Eden1" and
"Eden2" make more
sense than your suggestions.

On Wed, 18 Feb 2004, Svetlana Eden wrote:
> Hi, everybody.
> This was an interesting discussion last time and it helped me a lot.
> 
> Could you please have a look at some feature and tell me
> why it was designed this way
> (my questions are under #########)
> 
> > x = c(1, 10)
> > y = c(99, 55)
> > d <- data.frame(x = x, y = y)
> > d
>    x  y
> 1  1 99
> 2 10 55
> > add <- data.frame(x = 14, y = 99)
> > add
>    x  y
> 1 14 99
> > d <- rbind(d, add)
> > d
>     x  y
> 1   1 99
> 2  10 55
> 11 14 99
> ######### it would be more natural to index the rows: 1,2,3 instead of
> #1,2,11  ?!
> >
> > d[3,1]
> [1] 14
> > d[11,1]
> [1] NA
> ######### especially if index '11' is not functioning...
You need "11": it is a row name and not a row index.
> > add1 <- data.frame(x = 10, y = 87)
> > d <- rbind(d, add)
> ######### now I would think that the next index should be 21, BUT:
> > d
>     x  y
> 1   1 99
> 2  10 55
> 11 14 99
> 12 10 87
> ######### so what is the intuition of such indexing?
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

Svetlana Eden <svetlana.eden at vanderbilt.edu> writes:
> Hi, everybody.
> This was an interesting discussion last time and it helped me a lot.
> 
> Could you please have a look at some feature and tell me
> why it was designed this way
> (my questions are under #########)
> 
> > x = c(1, 10)
> > y = c(99, 55)
> > d <- data.frame(x = x, y = y)
> > d
>    x  y
> 1  1 99
> 2 10 55
> > add <- data.frame(x = 14, y = 99)
> > add
>    x  y
> 1 14 99
> > d <- rbind(d, add)
> > d
>     x  y
> 1   1 99
> 2  10 55
> 11 14 99
> ######### it would be more natural to index the rows: 1,2,3 instead of
> #1,2,11  ?!
It's not the number 11, it is the string "11".

Row names are character strings.  In your original data frame the row
names were "1" and "2" for the first frame and "1"
for the second.
The rbind function should not create a duplicate row name so it
prepended a "1" to all the names in the second frame.  That explains
the "11" and "12" in your last example.  They are simply the
original
names "1" and "2" with a "1" prepended to them.
> >
> > d[3,1]
> [1] 14
> > d[11,1]
Try d["11", 1]
> [1] NA
> ######### especially if index '11' is not functioning...
> >
> > add1 <- data.frame(x = 10, y = 87)
> > d <- rbind(d, add)
> ######### now I would think that the next index should be 21, BUT:
> > d
>     x  y
> 1   1 99
> 2  10 55
> 11 14 99
> 12 10 87
> ######### so what is the intuition of such indexing?

Svetlana Eden wrote:
> Hi, everybody.
> This was an interesting discussion last time and it helped me a lot.
> 
> Could you please have a look at some feature and tell me
> why it was designed this way
What you see in the first column are the row names. The index is 1,2,3,4 
as usual.

Thomas P.

Interesting feature
The logic seems to be simple. The first digit in the label indicates the row

position within the new matrix/vector that is being added.  Thus the first
digit remains 1
if you go on adding single rows. The second digit is then filled up by the
lowest digit 
possible that makes the label distinct from all previous labels, and the
third so on.... 
Try adding not just single rows but matrices of more than 1 rows repeatedly,

and the pattern will be clear.
 
Supratik. 

	[[alternative HTML version deleted]]

Hi!

On Wed, Feb 18, 2004 at 10:45:23AM -0600, Svetlana Eden
wrote:
> > d <- rbind(d, add)
> > d
>     x  y
> 1   1 99
> 2  10 55
> 11 14 99
> ######### it would be more natural to index the rows: 1,2,3 instead of
> #1,2,11  ?!
What you see in the first column are row-names not indexes. Since both
data frames had a row named '1' there was a conflict which R is trying
to resolve by appending '1'.
> ######### especially if index '11' is not functioning...
...
> ######### now I would think that the next index should be 21, BUT:
...
> ######### so what is the intuition of such indexing?
I think it all becomes clear if you try this:
> a <- data.frame(foo=1:5, bar=10:6, row.names=LETTERS[1:5])
> a
  foo bar
A   1  10
B   2   9
C   3   8
D   4   7
E   5   6
> b <- data.frame(foo=c(9,10), bar=c(99,98),
row.names=c('A','B'))
> b
  foo bar
A   9  99
B  10  98
> rbind(a,b)
   foo bar
A    1  10
B    2   9
C    3   8
D    4   7
E    5   6
A1   9  99
B1  10  98

cu
	Philipp

-- 
Dr. Philipp Pagel                                Tel.  +49-89-3187-3675
Institute for Bioinformatics / MIPS              Fax.  +49-89-3187-3585
GSF - National Research Center for Environment and Health
Ingolstaedter Landstrasse 1
85764 Neuherberg, Germany
http://mips.gsf.de/~pagel

> From: Svetlana Eden
> 
> Hi, everybody.
> This was an interesting discussion last time and it helped me a lot.
> 
> Could you please have a look at some feature and tell me
> why it was designed this way
> (my questions are under #########)
I give it a shot...
 
> > x = c(1, 10)
> > y = c(99, 55)
> > d <- data.frame(x = x, y = y)
> > d
>    x  y
> 1  1 99
> 2 10 55
> > add <- data.frame(x = 14, y = 99)
> > add
>    x  y
> 1 14 99
> > d <- rbind(d, add)
> > d
>     x  y
> 1   1 99
> 2  10 55
> 11 14 99
> ######### it would be more natural to index the rows: 1,2,3 instead of
> #1,2,11  ?!
rownames for data.frame need not be 1, 2, ..., and we need something that's
going to work regardless.
> > d[3,1]
> [1] 14
> > d[11,1]
> [1] NA
> ######### especially if index '11' is not functioning...
This one seems curious to me.  Trying to access non-existing column result
in error:
> d[1,11]
Error in "[.data.frame"(d, 1, 11) : undefined columns selected

OTOH, try:
> d[11,1] <- 1
> dim(d)
[1] 11  2
> d
Error in data.frame(x = c(" 1", "10", "14",
"NA", "NA", "NA", "NA", "NA", 
:

        duplicate row.names: 11

so that destroys the integrity of the data frame!
> > add1 <- data.frame(x = 10, y = 87)
> > d <- rbind(d, add)
> ######### now I would think that the next index should be 21, BUT:
> > d
>     x  y
> 1   1 99
> 2  10 55
> 11 14 99
> 12 10 87
> ######### so what is the intuition of such indexing?
I believe the rationale is explained in ?make.unique (which
rbind.data.frame() calls to create the rownames).
 
HTH,
Andy

 
> -- 
> Svetlana Eden        Biostatistician II            School of Medicine
>                      Department of Biostatistics   Vanderbilt 
> University
> 
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