Hi Jose, I'm answering your second batch of questions, since Chuck Berry has already well done so with the first one
>>>>> "Jose" == Jose Quesada <[EMAIL PROTECTED]> >>>>> on Tue, 23 Jan 2007 21:46:27 +0100 writes: [........] Jose> # example Jose> library(Matrix) Jose> x = as(x,"CsparseMatrix") [..........] Jose> Also, I have noticed that getting a row from a Matrix Jose> object produces a normal array (i.e., it does not Jose> inherit Matrix class). This is very much on purpose, following the principle of "least surprise" so I'm surprised you're suprised.. : The 'Matrix' behavior has been modelled to follow the more than 20 years old 'matrix' behavior : > matrix(1:9, 3) [,2] [1] 4 5 6 > matrix(1:9, 3) [,2 , drop=FALSE] [,1] [1,] 4 [2,] 5 [3,] 6 > library(Matrix) Loading required package: lattice > Matrix(1:9, 3) [,2] [1] 4 5 6 > Matrix(1:9, 3) [,2, drop = FALSE] 3 x 1 Matrix of class "dgeMatrix" [,1] [1,] 4 [2,] 5 [3,] 6 > But then I should not be surprised, because there has been the R FAQ >> 7.5 Why do my matrices lose dimensions? for quite a while. *And* I think that there is only one "thing" in the S language about which every "knowledgable one" agrees that it's a "design bug", and that's the fact that 'drop = TRUE' is the default, and not 'drop = FALSE' {but it's not possible to change now, please don't start that discussion!} Given what I say above, I wonder if our ("new-style") 'Matrix' objects should not behave differently than ("old-style") 'matrix' and indeed do use a default 'drop = FALSE'. This might break some Matrix-based code though, but then 'Matrix' is young enough, and working Matrix indexing is much younger, and there are only about 4 CRAN/Bioconductor packages depending on 'Matrix'. --> This discussion (about changing this behavior in the "Matrix" package) should definitely be lead on the R-devel mailing list --> CC'ing to R-devel {hence one (but please *only* one !) cross-post} Jose> However, selecting >1 rows, Jose> does produce a same-class matrix. If I convert with Jose> as() the output of selecting one row, am I losing Jose> performance? Is there any way to make the resulting Jose> vector be a 1-D Matrix object? yes, ", drop = FALSE", see above Martin ______________________________________________ R-help@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.