Hi Austin, What version of R are you using? It works for me for R 2.10.0 Patched on Win XP Pro:
R> a <- matrix(c(1, 2, 3, 4), nrow = 2) R> a # [1] 1 3 # [2] 2 4 R> rmask <- c(TRUE, FALSE) R> a[rmask,] # [1] 1 3 HTH, Jorge On Fri, Dec 4, 2009 at 3:52 PM, Austin Huang <> wrote: > One problem I've been having is the special case in which only one > row/column remains and the variable gets converted into a vector when > entries are removed by logical masking. This is a problem because > subsequent > code may rely on matrix operations (apply, colsums, dim, etc) For example: > > > a <- matrix(c(1, 2, 3, 4), nrow = 2) > > a > [,1] [,2] > [1,] 1 3 > [2,] 2 4 > > rmask <- c(TRUE, FALSE) > > b <- a[rmask, ] > > colSums(b) > Error in colSums(b) : 'x' must be an array of at least two dimensions > > To ensure the code works regardless of how the matrix gets modified, I need > to explicitly recast results to a matrix, for example: > > b <- matrix(a[rmask, ], ncol = 2) > > This can get messy, requiring extra work to maintain column/row names or > additional commands to determine the correct dimensions of the matrix (for > example, if I'm masking both rows and columns simultaneously). Is there a > more elegant way to deal with this in R? > > ~A > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org 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. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org 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.
