try this:
match.pat <- function (mat, target, nomatch = -1) {
f1 <- do.call("paste", c(as.data.frame(mat), sep = "\r"))
f2 <- paste(target, collapse = "\r")
ind <- f1 %in% f2
if (any(ind)) which(ind)[1] else nomatch
}
##################
set.seed(1234)
mat <- matrix(sample(0:1, 50, TRUE), 10, 5)
targ1 <- mat[2, ]
match.pat(mat, targ1)
targ2 <- rep(0, 5)
match.pat(mat, targ2)
I hope it helps.
Best,
Dimitris
----
Dimitris Rizopoulos
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm
----- Original Message -----
From: "Esmail Bonakdarian" <[EMAIL PROTECTED]>
To: <r-help@r-project.org>
Sent: Wednesday, June 11, 2008 1:58 PM
Subject: [R] searching for specific row in matrix
Hi,
I have matrix of bits and a target vector. Is there an
efficient way to search the rows of the matrix for the target?
I am interested in the first row index where target is found.
Example:
> source("lookup.R")
[,1] [,2] [,3] [,4] [,5]
[1,] 1 0 1 1 0
[2,] 1 1 0 1 0
[3,] 0 0 1 0 0
[4,] 1 0 0 1 1
[5,] 1 0 1 1 1
[6,] 1 1 0 0 1
[7,] 1 0 0 1 1
[8,] 0 0 1 1 1
[9,] 0 1 1 0 1
[10,] 0 0 0 1 0
target: 1 1 0 1 1
Should return -1 (or some other indicator) since the
target was not found in any of the rows.
> source("lookup.R")
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 1 1 0
[2,] 1 0 0 0 0
[3,] 1 0 0 0 0
[4,] 1 1 0 0 0
[5,] 1 1 1 0 0
[6,] 0 0 1 1 0
[7,] 0 1 1 1 0
[8,] 0 0 1 1 0
[9,] 1 1 0 1 1
[10,] 1 0 1 0 0
target: 1 1 0 1 1
Should return 9 since the target was found in row 9
If the target is found, it is no longer necessary to keep
searching the rest of the matrix (which may be quite large)
The data/size etc may change of course, but target will
always have the same number of "columns" as the matrix.
I tried variations of "which", and a for loop
comparing pop[i,] to target without much success, nor
did google yield any results. I am hoping someone here
can provide a suggestion.
Thanks,
EB
---------------------------------------------
# Here is the code that generates the above data
create_bin_string <- function(len)
{
sample(0:1, len, replace=T)
}
ROWS = 10
COLS = 5
pop = matrix(create_bin_string(ROWS*COLS), ROWS, COLS, byrow=T)
target=c(1, 1, 0, 1, 1)
# my population
print(pop)
# I am looking for the index of this in pop
# if present (else -1?)
cat("\ntarget: ", target, "\n")
##
## this is NOT working
## plus it would continue to search
## after it found the target
##
for(i in ROWS)
if (pop[i,] == target)
cat("\nfound in row: ", i, "\n\n")
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
