R help - Jan 2012 - finding rows in a matrix that match a vector

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:
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Sent from the R help mailing list archive at Nabble.com.

Hi,

Please excuse my inexperience, 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 something like this, but I don't know what function I am supposed to 
input into 'apply' to use this.

Thanks in advance for the help!

Cheers,
Melissa

-- 
Melissa Patrician
School of Marine and Atmospheric Sciences
Stony Brook University
Stony Brook, NY 11794-5000
Challenger 145
melissa.patrician@stonybrook.edu


	[[alternative HTML version deleted]]

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.
>
>______________________________________________
>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.