R help - Dec 2009 - Remove rows in a matrix that match rows in another matrix

Dear R Community,

The following seems like a simple problem, but I''ve been stuck on it
for
some time, with no luck using matching or subsetting functions.  I''m
trying
to remove the rows from a large matrix that match rows in another large
matrix.  A (small scale) example:

col1<-c("A", "B", "C", "D")
col2<-c("A", "B", "C", "D")
m1<-cbind(col1, col2)
col3<-c("B", "C", "D")
col4<-c("B", "C", "z")
m2<-cbind(col3, col4)

Any ideas on how to get the following matrix?
     [,1] [,2]
[1,] "A"  "A" 
[2,] "D"  "D" 

Thanks very much in advance,
Ray


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On Dec 19, 2009, at 11:11 PM, Raymond Danner wrote:
> Dear R Community,
>
> The following seems like a simple problem, but I've been stuck on it  
> for
> some time, with no luck using matching or subsetting functions.  I'm  
> trying
> to remove the rows from a large matrix that match rows in another  
> large
> matrix.  A (small scale) example:
>
> col1<-c("A", "B", "C", "D")
> col2<-c("A", "B", "C", "D")
> m1<-cbind(col1, col2)
> col3<-c("B", "C", "D")
> col4<-c("B", "C", "z")
> m2<-cbind(col3, col4)
>
> Any ideas on how to get the following matrix?
>     [,1] [,2]
> [1,] "A"  "A"
> [2,] "D"  "D"
>
I have an idea but I don't claim it to be the most elegant"

apply(m1, 1, function(x) max( apply(m2, 1, function(y) all.equal(x, y,  
check.attributes=FALSE)) ) ) != "TRUE"
[1]  TRUE FALSE FALSE  TRUE

So....using logical indexing...

m1[apply(m1, 1, function(x) max(    # max(c(TRUE,FALSE))==TRUE
               apply(m2, 1, function(y)   # now cycle through all of  
2nd mtx
                   all.equal(x, y, check.attributes=FALSE)) ) ) !=  
"TRUE" , ]

Last logical test "inverts" the result so you get the non-matched
rows.

      col1 col2
[1,] "A"  "A"
[2,] "D"  "D"

all.equal is set up to allow ignoring the attributes (col names)  
whereas identical did not appear to allow that
> Thanks very much in advance,
> Ray
>
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at 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.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Raymond Danner
> Sent: Saturday, December 19, 2009 8:12 PM
> To: r-help at r-project.org
> Subject: [R] Remove rows in a matrix that match rows in another matrix
> 
> Dear R Community,
> 
> The following seems like a simple problem, but I've been 
> stuck on it for
> some time, with no luck using matching or subsetting 
> functions.  I'm trying
> to remove the rows from a large matrix that match rows in 
> another large
> matrix.  A (small scale) example:
> 
> col1<-c("A", "B", "C", "D")
> col2<-c("A", "B", "C", "D")
> m1<-cbind(col1, col2)
> col3<-c("B", "C", "D")
> col4<-c("B", "C", "z")
> m2<-cbind(col3, col4)
> 
> Any ideas on how to get the following matrix?
>      [,1] [,2]
> [1,] "A"  "A" 
> [2,] "D"  "D" 
One way is to paste together the columns to make
a 'key' for the row and use match() or is.element()
on the key.  E.g.,
  > key <- function(m)paste(sep="\1",m[,1],m[,2])
  > m1[!is.element(key(m1),key(m2)),]
       col1 col2
  [1,] "A"  "A" 
  [2,] "D"  "D" 

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com  
> 
> Thanks very much in advance,
> Ray
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at 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.
>