

I want to compare two matrices or data frames and select or get an index for those rows which are the same in both. I have tried the following :
a = matrix ( 1:10, ncol = 2 )
a
b = matrix ( c ( 2,3,4,7,8,9 ), ncol = 2 )
b
a[a==b]
a = as.data.frame ( matrix ( 1:10, ncol = 2 ) )
a
b = as.data.frame ( matrix ( c ( 2,3,4,7,8,9 ), ncol = 2 ) )
b
a[a==b]
Any ideas please.
Thanks.
Simon Parker
Imperial College


I'm not sure what you want, but take a look at ?merge and %in%
ppaarrkk wrote
I want to compare two matrices or data frames and select or get an index for those rows which are the same in both. I have tried the following :
a = matrix ( 1:10, ncol = 2 )
a
b = matrix ( c ( 2,3,4,7,8,9 ), ncol = 2 )
b
a[a==b]
a = as.data.frame ( matrix ( 1:10, ncol = 2 ) )
a
b = as.data.frame ( matrix ( c ( 2,3,4,7,8,9 ), ncol = 2 ) )
b
a[a==b]
Any ideas please.
Thanks.
Simon Parker
Imperial College


Dear Simon,
Try this:
# Index  FALSE, TRUE
sapply(1:nrow(a),function(x) all(a[x,]%in%b))
# Rows of a that are in b
which(sapply(1:nrow(a),function(x) all(a[x,]%in%b)))
# Reporting
a[sapply(1:nrow(a),function(x) all(a[x,]%in%b)),]
HTH,
Jorge
On Tue, Dec 9, 2008 at 9:57 AM, ppaarrkk < [hidden email]> wrote:
>
> I want to compare two matrices or data frames and select or get an index
> for
> those rows which are the same in both. I have tried the following :
>
>
>
>
>
>
> a = matrix ( 1:10, ncol = 2 )
> a
>
> b = matrix ( c ( 2,3,4,7,8,9 ), ncol = 2 )
> b
>
> a[a==b]
>
>
>
>
>
>
> a = as.data.frame ( matrix ( 1:10, ncol = 2 ) )
> a
>
> b = as.data.frame ( matrix ( c ( 2,3,4,7,8,9 ), ncol = 2 ) )
> b
>
> a[a==b]
>
>
>
>
>
>
>
>
> Any ideas please.
>
>
> Thanks.
>
>
> Simon Parker
> Imperial College
>
> 
> View this message in context:
> http://www.nabble.com/Selectingrowsthatarethesameinseparatedataframestp20916243p20916243.html> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/rhelp> PLEASE do read the posting guide
> http://www.Rproject.org/postingguide.html> and provide commented, minimal, selfcontained, reproducible code.
>
[[alternative HTML version deleted]]
______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/rhelpPLEASE do read the posting guide http://www.Rproject.org/postingguide.htmland provide commented, minimal, selfcontained, reproducible code.


Try this:
1) Rows:
merge(as.data.frame(a), as.data.frame(b), sort = FALSE)
2) Index:
merge(cbind(as.data.frame(a), Idx = 1:nrow(a)), as.data.frame(b), sort =
FALSE)$Idx
On Tue, Dec 9, 2008 at 12:57 PM, ppaarrkk < [hidden email]> wrote:
>
> I want to compare two matrices or data frames and select or get an index
> for
> those rows which are the same in both. I have tried the following :
>
>
>
>
>
>
> a = matrix ( 1:10, ncol = 2 )
> a
>
> b = matrix ( c ( 2,3,4,7,8,9 ), ncol = 2 )
> b
>
> a[a==b]
>
>
>
>
>
>
> a = as.data.frame ( matrix ( 1:10, ncol = 2 ) )
> a
>
> b = as.data.frame ( matrix ( c ( 2,3,4,7,8,9 ), ncol = 2 ) )
> b
>
> a[a==b]
>
>
>
>
>
>
>
>
> Any ideas please.
>
>
> Thanks.
>
>
> Simon Parker
> Imperial College
>
> 
> View this message in context:
> http://www.nabble.com/Selectingrowsthatarethesameinseparatedataframestp20916243p20916243.html> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/rhelp> PLEASE do read the posting guide
> http://www.Rproject.org/postingguide.html> and provide commented, minimal, selfcontained, reproducible code.
>

Henrique Dallazuanna
CuritibaParanáBrasil
25° 25' 40" S 49° 16' 22" O
[[alternative HTML version deleted]]
______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/rhelpPLEASE do read the posting guide http://www.Rproject.org/postingguide.htmland provide commented, minimal, selfcontained, reproducible code.


Thanks for reply.
What I want is the equivalent of this :
xxx = 1:10
which(xxx %in% c(2,5))
.......but where there is more than one criterion for matching.
which (b %in% a) in the code I included does nothing (not surprisingly).
I'm not sure that I can use merge, because I want the whole of a, but to mark those rows which are also in b. If I do merge ( a,b ), I just get b. If I do merge ( a,b, all.x =TRUE), I get a.
bartjoosen wrote
I'm not sure what you want, but take a look at ?merge and %in%
ppaarrkk wrote
I want to compare two matrices or data frames and select or get an index for those rows which are the same in both. I have tried the following :
a = matrix ( 1:10, ncol = 2 )
a
b = matrix ( c ( 2,3,4,7,8,9 ), ncol = 2 )
b
a[a==b]
a = as.data.frame ( matrix ( 1:10, ncol = 2 ) )
a
b = as.data.frame ( matrix ( c ( 2,3,4,7,8,9 ), ncol = 2 ) )
b
a[a==b]
Any ideas please.
Thanks.
Simon Parker
Imperial College

