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aubert@inapg.fr

2004-Jul-08 07:20 UTC

[R] Problem with the grep function

Let me present to you my problem :

I have a character vector x and I would like to  obtain the indices of the 
elements of
this vector that yielded exactly a match.

For example,  x=nom, pattern="b", I would to obtain 2 because
"b" is on the
second position.

First program :
nom <- c("a","b","ab")
grep("b",nom)
2 3

Then I try the option extended =FALSE (instead of TRUE by default) and I 
obtain '2 3' a second time.

Please can you help me : How can I obtain only 2 in using the grep function 
(without using the match function).

Thanks you

Julie AUBERT

Wolski

2004-Jul-08 07:36 UTC

head link

[R] Problem with the grep function

Hi!

For exact matches you can use
== or is.element.
To get the indices use which.

e.g. => x<-c("a","b","ab")
> x=="a"
[1]  TRUE FALSE FALSE> which((x=="a")==T)[1] 1

or

e.g. is.element
> is.element(x,"a")
[1]  TRUE FALSE FALSE> which(is.element(x,"a")==TRUE)
[1] 1> 
Sincerely
Eryk


*********** REPLY SEPARATOR  ***********

On 7/8/2004 at 9:20 AM aubert at inapg.fr wrote:
>>>Let me present to you my problem :
>>>
>>>I have a character vector x and I would like to  obtain the indices
of
>>>the 
>>>elements of
>>>this vector that yielded exactly a match.
>>>
>>>For example,  x=nom, pattern="b", I would to obtain 2
because "b" is on
>>>the 
>>>second position.
>>>
>>>First program :
>>>nom <- c("a","b","ab")
>>>grep("b",nom)
>>>2 3
>>>
>>>Then I try the option extended =FALSE (instead of TRUE by default)
and I
>>>obtain '2 3' a second time.
>>>
>>>Please can you help me : How can I obtain only 2 in using the grep
>>>function 
>>>(without using the match function).
>>>
>>>Thanks you
>>>
>>>Julie AUBERT
>>>
>>>______________________________________________
>>>R-help at stat.math.ethz.ch mailing list
>>>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>>>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html


Dipl. bio-chem. Eryk Witold Wolski    @    MPI-Moleculare Genetic   
Ihnestrasse 63-73 14195 Berlin       'v'    
tel: 0049-30-83875219               /   \    
mail: wolski at molgen.mpg.de        ---W-W----   
http://www.molgen.mpg.de/~wolski

Alec Stephenson

2004-Jul-08 07:41 UTC

head link

[R] Problem with the grep function

grep("^b$",nom) will match "b" only.

Alec


Alec Stephenson                                               
Department of Statistics
Macquarie University
NSW 2109, Australia 
>>> "aubert at inapg.fr" <aubert at inapg.fr> 07/08/04
05:20pm >>>Let me present to you my problem :

I have a character vector x and I would like to  obtain the indices of
the 
elements of
this vector that yielded exactly a match.

For example,  x=nom, pattern="b", I would to obtain 2 because
"b" is on
the 
second position.

First program :
nom <- c("a","b","ab")
grep("b",nom)
2 3

Then I try the option extended =FALSE (instead of TRUE by default) and
I 
obtain '2 3' a second time.

Please can you help me : How can I obtain only 2 in using the grep
function 
(without using the match function).

Thanks you

Julie AUBERT

______________________________________________
R-help at stat.math.ethz.ch mailing list
https://www.stat.math.ethz.ch/mailman/listinfo/r-help 
PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html

aubert@inapg.fr

2004-Jul-08 07:43 UTC

head link

[R] Problem with the grep function

Hi Christian,

It works better now. Thanks a lot.

Julie

At 09:32 08/07/2004 +0200, you wrote:>Hi Julie,
>
>as I understand your question you only want indices for exact matches to
>"b". This can be achieved using regular expressions (see ?regex)
>
>nom <- c("a","b","ab")
>grep("^b$",nom)
>
>I hope this helps?
>
>Christian

Jan_Svatos@eurotel.cz

2004-Jul-08 07:47 UTC

head link

[R] Problem with the grep function

Hi Julie,

match is not exactly what you need, as it works with regular expressions 
and takes anything what includes a letter "b".
For your case, there is perfectly suitable

which(nom=="b")

nom <- c("a","b","ab", "b")
which(nom=="b")
[1] 2 4

Jan


- - - Original message: - - -
From: r-help-bounces at stat.math.ethz.ch
Send: 8.7.2004 9:24:58
To: r-help at stat.math.ethz.ch
Subject: [R] Problem with the grep function

Let me present to you my problem :

I have a character vector x and I would like to  obtain the indices of the
elements of
this vector that yielded exactly a match.

For example,  x=nom, pattern="b", I would to obtain 2 because
"b" is on
the
second position.

First program :
nom <- c("a","b","ab")
grep("b",nom)
2 3

Then I try the option extended =FALSE (instead of TRUE by default) and I
obtain '2 3' a second time.

Please can you help me : How can I obtain only 2 in using the grep 
function
(without using the match function).

Thanks you

Julie AUBERT

______________________________________________
R-help at stat.math.ethz.ch mailing list
https://www.stat.math.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! 
http://www.R-project.org/posting-guide.html

Wolski

2004-Jul-08 07:49 UTC

head link

[R] Problem with the grep function

Or you must mark the word beginning with ^ and the end $ if you like to use
grep.

grep("^b$",nom)


Sincerely
Eryk


*********** REPLY SEPARATOR  ***********

On 7/8/2004 at 9:20 AM aubert at inapg.fr wrote:
>>>Let me present to you my problem :
>>>
>>>I have a character vector x and I would like to  obtain the indices
of
>>>the 
>>>elements of
>>>this vector that yielded exactly a match.
>>>
>>>For example,  x=nom, pattern="b", I would to obtain 2
because "b" is on
>>>the 
>>>second position.
>>>
>>>First program :
>>>nom <- c("a","b","ab")
>>>grep("b",nom)
>>>2 3
>>>
>>>Then I try the option extended =FALSE (instead of TRUE by default)
and I
>>>obtain '2 3' a second time.
>>>
>>>Please can you help me : How can I obtain only 2 in using the grep
>>>function 
>>>(without using the match function).
>>>
>>>Thanks you
>>>
>>>Julie AUBERT
>>>
>>>______________________________________________
>>>R-help at stat.math.ethz.ch mailing list
>>>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>>>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html


Dipl. bio-chem. Eryk Witold Wolski    @    MPI-Moleculare Genetic   
Ihnestrasse 63-73 14195 Berlin       'v'    
tel: 0049-30-83875219               /   \    
mail: wolski at molgen.mpg.de        ---W-W----   
http://www.molgen.mpg.de/~wolski

Petr Pikal

2004-Jul-08 12:28 UTC

head link

[R] Problem with the grep function

Hi

You can use  %in%
> nom%in%"b"[1] FALSE  TRUE FALSE

which gives you a logical vector of exact matches
> (1:3)[nom%in%"b"][1] 2

or charmatch
> charmatch("b",nom)
[1] 2> charmatch("ab",nom)[1] 3

if you expect only one exact match.

But I expect someone can give you better answer.

Cheers
Petr

On 8 Jul 2004 at 9:20, aubert at inapg.fr wrote:
> Let me present to you my problem :
> 
> I have a character vector x and I would like to  obtain the indices of
> the elements of this vector that yielded exactly a match.
> 
> For example,  x=nom, pattern="b", I would to obtain 2 because
"b" is
> on the second position.
> 
> First program :
> nom <- c("a","b","ab")
> grep("b",nom)
> 2 3
> 
> Then I try the option extended =FALSE (instead of TRUE by default) and
> I obtain '2 3' a second time.
> 
> Please can you help me : How can I obtain only 2 in using the grep
> function (without using the match function).
> 
> Thanks you
> 
> Julie AUBERT
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
Petr Pikal
petr.pikal at precheza.cz

Marc Mamin

2004-Jul-09 08:55 UTC

head link

[R] Problem with the grep function

Hi,

you can use regular expression with grep. 

For example:
>exactmatch<-function(s,l){return(grep(paste('^',s,'$',sep=''),l))}
>t<-c('a','ab','abc','c','ca','ab')
> exactmatch('ab',t)[1] 2 6

HTH

Marc



-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of Petr Pikal
Sent: Thursday, July 08, 2004 2:28 PM
To: aubert at inapg.fr; r-help at stat.math.ethz.ch
Subject: Re: [R] Problem with the grep function


Hi

You can use  %in%
> nom%in%"b"[1] FALSE  TRUE FALSE

which gives you a logical vector of exact matches
> (1:3)[nom%in%"b"][1] 2

or charmatch
> charmatch("b",nom)
[1] 2> charmatch("ab",nom)[1] 3

if you expect only one exact match.

But I expect someone can give you better answer.

Cheers
Petr

On 8 Jul 2004 at 9:20, aubert at inapg.fr wrote:
> Let me present to you my problem :
> 
> I have a character vector x and I would like to  obtain the indices of
> the elements of this vector that yielded exactly a match.
> 
> For example,  x=nom, pattern="b", I would to obtain 2 because
"b" is
> on the second position.
> 
> First program :
> nom <- c("a","b","ab")
> grep("b",nom)
> 2 3
> 
> Then I try the option extended =FALSE (instead of TRUE by default) and
> I obtain '2 3' a second time.
> 
> Please can you help me : How can I obtain only 2 in using the grep
> function (without using the match function).
> 
> Thanks you
> 
> Julie AUBERT
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
Petr Pikal
petr.pikal at precheza.cz

______________________________________________
R-help at stat.math.ethz.ch mailing list
https://www.stat.math.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html

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