Dear R Users, I have a matrix A, and I want to change every value of this matrix if these values are greater than an assuming value. For a vector it is simple, e.g. a<-c(1:10); a[a>5]<-0. Of course, I can change matrix to vector, assign a value then change vector to matrix. But does there exist simpler way? Any suggestion are appreciate. Rob
robert-mcfadden at o2.pl wrote:> Dear R Users, > I have a matrix A, and I want to change every value of this matrix if these values are greater than an assuming value. For a vector it is simple, e.g. a<-c(1:10); a[a>5]<-0. > Of course, I can change matrix to vector, assign a value then change vector to matrix. But does there exist simpler way?The same syntax as for a vector: A[A>5] <- 0 Remember that matrices are just vectors with a dim attribute. The dim attribute is unchanged by this operation: > A <- matrix(1:10, 2, 5) > A [,1] [,2] [,3] [,4] [,5] [1,] 1 3 5 7 9 [2,] 2 4 6 8 10 > A[A>5] <- 0 > A [,1] [,2] [,3] [,4] [,5] [1,] 1 3 5 0 0 [2,] 2 4 0 0 0 Duncan Murdoch
Rob,
Try
a[a>5]<-0
Yup. It works for matrices (and for arrays). It also works with the
replacement value being a vector. For example, try
b <- array(1:24, dim=c(3, 4, 2))
b[(b>8) & (b<17)] <- 101:108
I think the reason it works like this is that internally array are stored
as vectors.
Cheers,
Andy
__________________________________
Andy Jaworski
518-1-01
Process Laboratory
3M Corporate Research Laboratory
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12/14/2006 08:01 [R] matrix - change values
AM
Dear R Users,
I have a matrix A, and I want to change every value of this matrix if these
values are greater than an assuming value. For a vector it is simple, e.g.
a<-c(1:10); a[a>5]<-0.
Of course, I can change matrix to vector, assign a value then change vector
to matrix. But does there exist simpler way?
Any suggestion are appreciate.
Rob
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R-help at stat.math.ethz.ch 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.
A matrix is already a vector, you don't need to do the transformations, just do the same thing directly:> tmp <- matrix( sample(1:12), ncol=3 ) > tmp[,1] [,2] [,3] [1,] 11 1 6 [2,] 3 7 9 [3,] 4 12 8 [4,] 2 5 10> tmp[tmp > 5] <- 0 > tmp[,1] [,2] [,3] [1,] 0 1 0 [2,] 3 0 0 [3,] 4 0 0 [4,] 2 5 0 If on the other hand, your matrix is really a data frame then functions like lapply, sapply, transform may help. Hope this helps, -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.snow at intermountainmail.org (801) 408-8111 -----Original Message----- From: r-help-bounces at stat.math.ethz.ch [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of robert-mcfadden at o2.pl Sent: Thursday, December 14, 2006 7:01 AM To: r-help at stat.math.ethz.ch Subject: [R] matrix - change values Dear R Users, I have a matrix A, and I want to change every value of this matrix if these values are greater than an assuming value. For a vector it is simple, e.g. a<-c(1:10); a[a>5]<-0. Of course, I can change matrix to vector, assign a value then change vector to matrix. But does there exist simpler way? Any suggestion are appreciate. Rob ______________________________________________ R-help at stat.math.ethz.ch 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.
I would like to thanks everybody for helpful suggestion. Rob Od: robert-mcfadden w o2.pl Do: r-help w stat.math.ethz.ch Data: 14 grudnia 2006 15:01 Temat: [R] matrix - change values> Dear R Users, > I have a matrix A, and I want to change every value of this matrix if these values are greater than an assuming value. For a vector it is simple, e.g. a<-c(1:10); a[a>5]<-0. > Of course, I can change matrix to vector, assign a value then change vector to matrix. But does there exist simpler way? > Any suggestion are appreciate. > Rob > > ______________________________________________ > R-help w stat.math.ethz.ch 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.