Hi, I would like to replace all the max values per row with "1" and all other values with "0". If there are two max values, then "0" for both. Example: from: 2 3 0 0 200 30 0 0 2 50 0 0 3 0 0 0 0 8 8 0 to: 0 0 0 0 1 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 Thanks! -- View this message in context: http://n4.nabble.com/How-to-replace-all-non-maximum-values-in-a-row-with-0-tp1819018p1819018.html Sent from the R help mailing list archive at Nabble.com.
Owe Jessen
2010-Apr-09 09:08 UTC
[R] How to replace all non-maximum values in a row with 0
Am 09.04.2010 10:04, schrieb burgundy:> Hi, > > I would like to replace all the max values per row with "1" and all other > values with "0". If there are two max values, then "0" for both. Example: > > from: > 2 3 0 0 200 > 30 0 0 2 50 > 0 0 3 0 0 > 0 0 8 8 0 > > to: > 0 0 0 0 1 > 0 0 0 0 1 > 0 0 1 0 0 > 0 0 0 0 0 > > Thanks! >Nice little homework to get the day started. :-) This worked for me, but is probably not the shortest possible answer A <- matrix (c(2, 3, 0, 0, 200, 30, 0, 0, 2, 50, 0, 0, 3, 0, 0, 0, 0, 8, 8, 0), nrow = 4, byrow=T) nr <- nrow(A) nc <- ncol(A) B <- matrix(0,nrow=nr, ncol=nc) for(i in 1:nr){ x <- which(A[i,]==max(A[i,])) B[i,x] <- 1 if(sum(B[i,])>1) B[i,] <- as.vector(rep(0,nc)) } -- Owe Jessen Nettelbeckstr. 5 24105 Kiel post at owejessen.de http://privat.owejessen.de
ONKELINX, Thierry
2010-Apr-09 09:25 UTC
[R] How to replace all non-maximum values in a row with 0
It can be done faster and more elegant with apply and rowSums
rows <- 100000
A <- matrix(rpois(n = rows * 20, lambda = 100), nrow = rows)
A[4, c(1,3)] <- 1000
system.time({
y <- t(apply(A, 1, function(z){
1 * (z == max(z))
}))
y[rowSums(y) > 1, ] <- 0
})
system.time({
nr <- nrow(A)
nc <- ncol(A)
B <- matrix(0,nrow=nr, ncol=nc)
for(i in 1:nr){
x <- which(A[i,]==max(A[i,]))
B[i,x] <- 1
if(sum(B[i,])>1) B[i,] <- as.vector(rep(0,nc))
}
})
all.equal(y, B)
HTH,
Thierry
------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek
team Biometrie & Kwaliteitszorg
Gaverstraat 4
9500 Geraardsbergen
Belgium
Research Institute for Nature and Forest
team Biometrics & Quality Assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be
www.inbo.be
To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data.
~ Roger Brinner
The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of
data.
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> -----Oorspronkelijk bericht-----
> Van: r-help-bounces at r-project.org
> [mailto:r-help-bounces at r-project.org] Namens Owe Jessen
> Verzonden: vrijdag 9 april 2010 11:08
> Aan: r-help at r-project.org
> Onderwerp: Re: [R] How to replace all non-maximum values in a
> row with 0
>
> Am 09.04.2010 10:04, schrieb burgundy:
> > Hi,
> >
> > I would like to replace all the max values per row with "1"
> and all other
> > values with "0". If there are two max values, then
"0" for
> both. Example:
> >
> > from:
> > 2 3 0 0 200
> > 30 0 0 2 50
> > 0 0 3 0 0
> > 0 0 8 8 0
> >
> > to:
> > 0 0 0 0 1
> > 0 0 0 0 1
> > 0 0 1 0 0
> > 0 0 0 0 0
> >
> > Thanks!
> >
> Nice little homework to get the day started. :-)
>
> This worked for me, but is probably not the shortest possible answer
>
> A <- matrix (c(2, 3, 0, 0, 200, 30, 0, 0, 2, 50, 0,
> 0, 3, 0,
> 0, 0, 0, 8, 8, 0), nrow = 4, byrow=T)
> nr <- nrow(A)
> nc <- ncol(A)
> B <- matrix(0,nrow=nr, ncol=nc)
> for(i in 1:nr){
> x <- which(A[i,]==max(A[i,]))
> B[i,x] <- 1
> if(sum(B[i,])>1) B[i,] <- as.vector(rep(0,nc))
> }
>
> --
> Owe Jessen
> Nettelbeckstr. 5
> 24105 Kiel
> post at owejessen.de
> http://privat.owejessen.de
>
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>
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Dennis Murphy
2010-Apr-09 16:47 UTC
[R] How to replace all non-maximum values in a row with 0
Hi:
This isn't much shorter than the previous solution, but here's another
take,
operating row-wise.
A <- matrix (c(2, 3, 0, 0, 200, 30, 0, 0, 2, 50, 0, 0, 3, 0, 0,
0, 0, 8, 8, 0), nrow = 4, byrow=T)
# Write a vector function to apply to each row: begin by initializing a zero
# vector of length = no. columns. Next, find which indices of the row vector
x
# match the maximum. If that number is >1, return a zero vector, else
replace
# the index where the maximum resides to 1.
f <- function(x) {
o <- rep(0, length(x))
w <- which(x == max(x))
r <- if(length(w) > 1) {o} else {
o[w] <- 1; o}
r
}
# Test:> t(apply(A, 1, f))
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 0 0 1
[2,] 0 0 0 0 1
[3,] 0 0 1 0 0
[4,] 0 0 0 0 0
HTH,
Dennis
On Fri, Apr 9, 2010 at 1:04 AM, burgundy <sauburn@yahoo.com> wrote:
>
> Hi,
>
> I would like to replace all the max values per row with "1" and
all other
> values with "0". If there are two max values, then "0"
for both. Example:
>
> from:
> 2 3 0 0 200
> 30 0 0 2 50
> 0 0 3 0 0
> 0 0 8 8 0
>
> to:
> 0 0 0 0 1
> 0 0 0 0 1
> 0 0 1 0 0
> 0 0 0 0 0
>
> Thanks!
> --
> View this message in context:
>
http://n4.nabble.com/How-to-replace-all-non-maximum-values-in-a-row-with-0-tp1819018p1819018.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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.
>
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