Hi, I was wondering if someone has witnessed the following behavior with matching on multiple minimums in a vector: If I manually create a vector of doubles: test <- c(2.33,11.09,0.02,0.02.1.7,6.41) I can then run any of the following to retrieve the indices of the minimum values (3 and 4 in this case), of which there are two (done purposefully): which(test==min(test)) or which(!is.na(match(test,min(test)))) or match(test,min(test)) # to see the entire vector However, my problem is as follows. I am not manually creating a vector to test for multiple minimums but rather doing a read.table on a file that contains the same data with other columns, etc. I then trim off the data from that matrix (there are several identical ways to do this): unlist(myMatrix[1], use.name=FALSE) or myMatrix[,1] But, running any of the tests listed above only returns the index of the last minimum. Both my manual vector and vector culled from the matrix appear to me to be identical (tested with is.vector, is.numeric, is.double, etc), but it will only every return the index of the second of the two minimums. Any help would be truly appreciated. Thanks Barry
matching on multiple minimums
3 messages · Barry Taylor, Brian Ripley, Adaikalavan Ramasamy
Please read ?"==" for comments and a suggested solution.
On Thu, 28 Oct 2004, Barry Taylor wrote:
Hi, I was wondering if someone has witnessed the following behavior with matching on multiple minimums in a vector: If I manually create a vector of doubles: test <- c(2.33,11.09,0.02,0.02.1.7,6.41) I can then run any of the following to retrieve the indices of the minimum values (3 and 4 in this case), of which there are two (done purposefully): which(test==min(test)) or which(!is.na(match(test,min(test)))) or match(test,min(test)) # to see the entire vector However, my problem is as follows. I am not manually creating a vector to test for multiple minimums but rather doing a read.table on a file that contains the same data with other columns, etc. I then trim off the data from that matrix (there are several identical ways to do this): unlist(myMatrix[1], use.name=FALSE) or myMatrix[,1] But, running any of the tests listed above only returns the index of the last minimum. Both my manual vector and vector culled from the matrix appear to me to be identical (tested with is.vector, is.numeric, is.double, etc), but it will only every return the index of the second of the two minimums. Any help would be truly appreciated.
Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
I cannot make sense of your question. There is no reproducible example
to help either. Please read the posting guide.
However, I think you might find using arr.ind=TRUE option in which()
when dealing with matrices to be useful. See help(which). Example :
mat <- matrix( 1:9, nc=3 ) + 100
mat[3,1] <- 101
mat
[,1] [,2] [,3]
[1,] 101 104 107
[2,] 102 105 108
[3,] 101 106 109
which( mat == min(mat), arr.ind=T )
row col
[1,] 1 1
[2,] 3 1
m1 <- mat[ ,1]
which( m1 == min(m1) )
[1] 1 3
On Thu, 2004-10-28 at 15:14, Barry Taylor wrote:
Hi, I was wondering if someone has witnessed the following behavior with matching on multiple minimums in a vector: If I manually create a vector of doubles: test <- c(2.33,11.09,0.02,0.02.1.7,6.41) I can then run any of the following to retrieve the indices of the minimum values (3 and 4 in this case), of which there are two (done purposefully): which(test==min(test)) or which(!is.na(match(test,min(test)))) or match(test,min(test)) # to see the entire vector However, my problem is as follows. I am not manually creating a vector to test for multiple minimums but rather doing a read.table on a file that contains the same data with other columns, etc. I then trim off the data from that matrix (there are several identical ways to do this): unlist(myMatrix[1], use.name=FALSE) or myMatrix[,1] But, running any of the tests listed above only returns the index of the last minimum. Both my manual vector and vector culled from the matrix appear to me to be identical (tested with is.vector, is.numeric, is.double, etc), but it will only every return the index of the second of the two minimums. Any help would be truly appreciated. Thanks Barry
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