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Esmail Bonakdarian

2008-Jun-11 11:58 UTC

[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")

Dimitris Rizopoulos

2008-Jun-11 12:52 UTC

head link

[R] searching for specific row in matrix

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" <esmail.js at gmail.com>
To: <r-help at 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")
>
> ______________________________________________
> 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.
> 

Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm

jim holtman

2008-Jun-11 13:01 UTC

head link

[R] searching for specific row in matrix

This should work for you:
> create_bin_string <- function(len)+ {
+  sample(0:1, len, replace=T)
+ }>
> ROWS = 10
> COLS =  5
> set.seed(2)
> pop = matrix(create_bin_string(ROWS*COLS), ROWS, COLS, byrow=T)
>
>
>
> target=c(1, 1, 0, 1, 1)
>
> # my population
> print(pop)      [,1] [,2] [,3] [,4] [,5]
 [1,]    0    1    1    0    1
 [2,]    1    0    1    0    1
 [3,]    1    0    1    0    0
 [4,]    1    1    0    0    0
 [5,]    1    0    1    0    0
 [6,]    0    0    0    1    0
 [7,]    0    0    1    1    1
 [8,]    1    1    0    1    0
 [9,]    1    0    0    0    1
[10,]    1    1    0    1    1>
> # determine which data matches
> matches <- t(pop) == target  # 't' due to matching in column
order
>
> # colSums equal to COLS will indicate matches
> which(colSums(matches) == COLS)
[1] 10>
On Wed, Jun 11, 2008 at 7:58 AM, Esmail Bonakdarian <esmail.js at
gmail.com> wrote:> 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")
>
> ______________________________________________
> 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.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

Henrique Dallazuanna

2008-Jun-11 13:05 UTC

head link

[R] searching for specific row in matrix

Try this:

which(apply(t(m) == target, 2, all))

On Wed, Jun 11, 2008 at 8:58 AM, Esmail Bonakdarian <esmail.js@gmail.com>
wrote:
> 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")
>
> ______________________________________________
> R-help@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.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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