[R] finding rows in a matrix that match a vector

[Florent D.]

Try this:

mine <- 1:6
table.combos <- matrix(data = 1:12, nrow = 10, ncol = 6, byrow)
row.is.a.match <- apply(table.combos, 1, identical, mine)
match.idx <- which(row.is.a.match)
total.matches <- sum(row.is.a.match)


On Sat, Jan 28, 2012 at 2:10 AM, Jason J. Pitt <pittjj at uchicago.edu> wrote:
>
> Hi Melissa,
>
> Well, assuming you know the length of the length of the row in
> the matrix and vector are the same... if you need a quick fix
> you could use
>
> mine <- 1:6
> table.combos <- matrix(data = 1:12, nrow = 2, ncol = 6, byrow
> = T)
>
> sum(mine == table.combos[1, ]) == length(mine)
> # returns TRUE
> sum(mine == table.combos[2, ]) == length(mine)
> #returns FALSE
>
> Though I'm sure there are more elegant and less error prone
> (if you don't know the lengths are equal) ways of doing this
> and others will point you in the right direction.
>
> Jason
>
> ---- Original message ----
> >Date: Fri, 27 Jan 2012 17:39:05 -0800 (PST)
> >From: r-help-bounces at r-project.org (on behalf of Melrose2012
> <melissa.patrician at stonybrook.edu>)
> >Subject: [R] finding rows in a matrix that match a vector
> >To: r-help at r-project.org
> >
> >Hi,
> >
> >Please excuse my ignorance, but I am just learning R (this is
> my very first
> >day programming in R) and having a really hard time figuring
> out how to do
> >the following:
> >
> >I have a matrix that is 1000 row by 6 columns (named
> 'table.combos') and a 1
> >row by 6 column vector (named 'mine').  I want to find every
> row in
> >'table.combos' that equals 'mine' and then count this number
> of times that
> >this is the case.
> >
> >In matlab, I would use the 'find' command but I can not seem
> to figure out
> >what syntax to use for R.
> >
> >Can anyone please help?
> >
> >Again, I'm assuming this is probably a very easy thing to do,
> but since I am
> >new to R, I am having a hard time figuring it out.  I did
> some research on
> >previous posts and saw that the 'apply' function appears to
> do osmething
> >like this, except I don't know what function I am supposed to
> input into
> >'apply' to use this.
> >
> >Thanks in advance for the help!
> >
> >Cheers,
> >Melissa
> >
> >--
> >View this message in context:
> http://r.789695.n4.nabble.com/finding-rows-in-a-matrix-that-
> match-a-vector-tp4335216p4335216.html
> >Sent from the R help mailing list archive at Nabble.com.
> >
> >______________________________________________
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> project.org/posting-guide.html
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> code.
>
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