R help - Mar 2009 - Selecting elements from a vector (a simple question with weird results)

Hello people.

I wish to reorder a simple vector of numbers by another vector of the order
(and then do the same, but with a data frame rows)

I try this (which doesn't work) :
> aa <- c(3, 1 ,2 )
> aa[aa]
[1] 2 3 1

The same won't work if I try to order a data frame:
> data.frame(matrix(c(3,1,2), 3,2))[c(3,1,2),]
  X1 X2
3  2  2
1  3  3
2  1  1


How should I do this?


p.s: sorry if the question is too simple, but I couldn't find a good
explanation for this on google.
p.p.s: I am running R 2.8


Thanks,
Tal

	[[alternative HTML version deleted]]

> I wish to reorder a simple vector of numbers by another vector of the order
> (and then do the same, but with a data frame rows)
> 
> I try this (which doesn't work) :
> > aa <- c(3, 1 ,2 )
> > aa[aa]
> [1] 2 3 1
> 
> The same won't work if I try to order a data frame:
> > data.frame(matrix(c(3,1,2), 3,2))[c(3,1,2),]
>   X1 X2
> 3  2  2
> 1  3  3
> 2  1  1
Looks like everything is working as expected to me. So maybe you should
explain what result you would like to get.

cu
	Philipp

-- 
Dr. Philipp Pagel
Lehrstuhl f?r Genomorientierte Bioinformatik
Technische Universit?t M?nchen
Wissenschaftszentrum Weihenstephan
85350 Freising, Germany
http://mips.gsf.de/staff/pagel

Thanks Patrick,
Sorry to have missed that!

Tal







On Sat, Mar 28, 2009 at 9:01 PM, Patrick Burns
<pburns@pburns.seanet.com>wrote:
> I presume you are looking for:
>
> aa[order(aa)]
>
> and
>
> df[order(df[,1]), ]
>
>
> Patrick Burns
> patrick@burns-stat.com
> +44 (0)20 8525 0696
> http://www.burns-stat.com
> (home of "The R Inferno" and "A Guide for the Unwilling S
User")
>
> Tal Galili wrote:
>
>> Hello people.
>>
>> I wish to reorder a simple vector of numbers by another vector of the
>> order
>> (and then do the same, but with a data frame rows)
>>
>> I try this (which doesn't work) :
>>
>>
>>> aa <- c(3, 1 ,2 )
>>> aa[aa]
>>>
>>>
>> [1] 2 3 1
>>
>> The same won't work if I try to order a data frame:
>>
>>
>>> data.frame(matrix(c(3,1,2), 3,2))[c(3,1,2),]
>>>
>>>
>>  X1 X2
>> 3  2  2
>> 1  3  3
>> 2  1  1
>>
>>
>> How should I do this?
>>
>>
>> p.s: sorry if the question is too simple, but I couldn't find a
good
>> explanation for this on google.
>> p.p.s: I am running R 2.8
>>
>>
>> Thanks,
>> Tal
>>
>>        [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>>
>>
>

-- 
----------------------------------------------


My contact information:
Tal Galili
Phone number: 972-50-3373767
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My Blogs:
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http://www.talgalili.com
http://www.biostatistics.co.il

	[[alternative HTML version deleted]]

Dear Tal,
It works as it should. In this code:

# Data
aa <- c(3, 1 ,2 )
aa
[1] 3 1 2

aa[aa]
[1] 2 3 1

you are telling R to do the following:  take the vector aa and select the
elements aa (in R language that is aa[aa]). If you look carefully, the third
element of aa is 2, the first is 3 and the second is 1.

Perhaps I'm missing something but, to me, it works as expected.  What would
you like to get?

HTH,

Jorge


On Sat, Mar 28, 2009 at 1:48 PM, Tal Galili <tal.galili@gmail.com> wrote:
> Hello people.
>
> I wish to reorder a simple vector of numbers by another vector of the order
> (and then do the same, but with a data frame rows)
>
> I try this (which doesn't work) :
> > aa <- c(3, 1 ,2 )
> > aa[aa]
> [1] 2 3 1
>
> The same won't work if I try to order a data frame:
> > data.frame(matrix(c(3,1,2), 3,2))[c(3,1,2),]
>  X1 X2
> 3  2  2
> 1  3  3
> 2  1  1
>
>
> How should I do this?
>
>
> p.s: sorry if the question is too simple, but I couldn't find a good
> explanation for this on google.
> p.p.s: I am running R 2.8
>
>
> Thanks,
> Tal
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

Tal Galili <tal.galili at gmail.com> [Sat, Mar 28, 2009 at 06:48:36PM
CET]:
> Hello people.
> 
> I wish to reorder a simple vector of numbers by another vector of the order
> (and then do the same, but with a data frame rows)
> 
> I try this (which doesn't work) :
> > aa <- c(3, 1 ,2 )
> > aa[aa]
> [1] 2 3 1
To my mind, it does what you told it to, and therefore "works"
in my book. The routine orders the numbers by placing the third element
first, the first second, and the second third.

Maybe aa[order(aa)] does what you mean it to do?

Best wishes


Johannes

-- 
Johannes H?sing               There is something fascinating about science. 
                              One gets such wholesale returns of conjecture 
mailto:johannes at huesing.name  from such a trifling investment of fact.
http://derwisch.wikidot.com         (Mark Twain, "Life on the
Mississippi")