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
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David Winsemius, MD
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