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"diag", "diag<-" and "[" , "[<-"
2 messages · bergarog at gmail.com, Duncan Murdoch
On 07/01/2010 9:31 AM, bergarog at gmail.com wrote:
Dear all I have the following problem. M <- matrix(0,3,3) # dimension of M is dinamic and this can lead to the next subscript diag(M[1,1]) <- rep(100,1) #Error in `diag<-`(`*tmp*`, value = 100) : # only matrix diagonals can be replaced diag(M[1,1,drop=F]) <- rep(100,1) #Error in diag(M[1, 1, drop = F]) <- rep(100, 1) : # incorrect number of subscripts diag(M[2:3,1:2]) <- rep(100,2) # works fine Is there a way to usw diag as replacement function when the input matrix is subscript to a one by one matrix. I don't want extra if(dim==1)... etc.
The problem isn't with diag, it's with "[<-". When you include drop=F,
it doesn't appear to handle properly the matrix indexing that diag() uses.
So a simpler example is just
M[1,1, drop=FALSE] <- 1
which generates the same error you saw. I'd call this a bug; I'll look
into it. ("[<-" is done internally in some fairly ugly code, so this
might take a while.)
As a workaround, I think this does what you want:
n <- 1
submatrix <- M[1:n,1:n,drop=FALSE]
diag(submatrix) <- rep(100, n)
M[1:n,1:n] <- submatrix
Duncan Murdoch
Thanks a lot in advance. Best regards, Roger [[alternative HTML version deleted]]
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