[R] expm() within the Matrix package

[Martin Maechler]

>>>>> "Gad" == Gad Abraham <g.abraham at ms.unimelb.edu.au>
>>>>>     on Mon, 19 Mar 2007 09:36:15 +1100 writes:

    Gad> If you convert to numeric, you can then assign it to Loglik:
    >> >> Loglik[1] <- as.numeric(log(p %*% expm(Q * y[i]) %*% q))
    >> >> Loglik[1]
    Gad> [1] 134.5565
    >> 
    >> 
    >> Hmm, I don't think that's Laura's problem
    >> (and actually I don't know what her problem is) :
    >> 
    >> Assignment of a 1 x 1 matrix to a vector is not a problem,
    >> and hence the  as.numeric(.) above  really has no effect :
    >> 
    >>> ll <- 1:2
    >>> (m <- matrix(pi, 1,1))
    >> [,1]
    >> [1,] 3.141593
    >>> ll[1] <- m
    >>> ll
    >> [1] 3.141593 2.000000

    Gad> Ah but you're using 'matrix' while she's using 'Matrix'
    Gad> (AFAIK there is no expm for matrix):


Yes, of course, you are absolutely right
(and I'm pretty embarrassed).

Martin

    >> library(Matrix)

    Gad> Loading required package: lattice
    >> m <- Matrix(1, nrow=1, ncol=1)
    >> m
    Gad> 1 x 1 diagonal matrix of class "ddiMatrix"
    Gad> [,1]
    Gad> [1,]    1
    Gad> Warning message:
    Gad> Ambiguous method selection for "diag", target "ddiMatrix" (the first of 
    Gad> the signatures shown will be used)
    Gad> diagonalMatrix
    Gad> ddenseMatrix
    Gad> in: .findInheritedMethods(classes, fdef, mtable)
    >> a <- vector("numeric", 0)
    >> a[1] <- m
    Gad> Error in a[1] <- m : incompatible types (from S4 to double) in 
    Gad> subassignment type fix
    >> a[1] <- as.numeric(m)
    >> a
    Gad> [1] 1

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