Dear list, The Matrix package exhibits some unexpected behaviour in its arithmetic methods for the edge case of a sparse matrix with a dimension of zero length. The example below is the most illustrative, where changing the contents of the vector causes the subtraction to fail for a sparse matrix with no columns: > library(Matrix) > x <- rsparsematrix(10, 0, density=0.1) > > x - rep(1, nrow(x)) # OK > x - rep(0, nrow(x)) # fails Error in .Ops.recycle.ind(e1, len = l2) : vector too long in Matrix - vector operation
This is presumably because Matrix recognizes that subtraction of zero preserves sparsity and thus uses a different method in the second case. However, I would have expected subtraction of a zero vector to work if subtraction of a general vector is permissible. This is accompanied by a host of related errors for sparsity-preserving arithmetic: > x / 1 # OK > x / rep(1, nrow(x)) # fails Error in .Ops.recycle.ind(e1, len = l2) : vector too long in Matrix - vector operation > > x * 1 # OK > x * rep(1, nrow(x)) # fails Error in .Ops.recycle.ind(e1, len = l2) : vector too long in Matrix - vector operation A different error is raised for a sparse matrix with no rows: > y <- rsparsematrix(0, 10, density=0.1) > > y - numeric(1) # OK > y - numeric(0) # fails Error in y - numeric(0) : <Matrix> - numeric(0) is undefined I would have expected to just get 'y' back, given that the same code works fine for other Matrix classes: > z <- as(y, "dgeMatrix") > z - numeric(0) # OK Correct behaviour of zero-dimension sparse matrices is practically important to me; I develop a number of packages that rely on Matrix classes, and in those packages, I do a lot of unit testing with zero- dimension inputs. This ensures that my functions return sensible results or fail gracefully in edge cases that might be encountered by users. The current behaviour of sparse Matrix arithmetic causes my unit tests to fail for no (obvious) good reason. Best, Aaron Lun Research Associate CRUK Cambridge Institute University of Cambridge > sessionInfo() R Under development (unstable) (2019-01-14 r75992) Platform: x86_64-pc-linux-gnu (64-bit) Running under: Ubuntu 16.04.5 LTS Matrix products: default BLAS: /home/cri.camres.org/lun01/Software/R/trunk/lib/libRblas.so LAPACK: /home/cri.camres.org/lun01/Software/R/trunk/lib/libRlapack.so locale: [1] LC_CTYPE=en_GB.UTF-8 LC_NUMERIC=C [3] LC_TIME=en_GB.UTF-8 LC_COLLATE=en_GB.UTF-8 [5] LC_MONETARY=en_GB.UTF-8 LC_MESSAGES=en_GB.UTF-8 [7] LC_PAPER=en_GB.UTF-8 LC_NAME=C [9] LC_ADDRESS=C LC_TELEPHONE=C [11] LC_MEASUREMENT=en_GB.UTF-8 LC_IDENTIFICATION=C attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] Matrix_1.2-15 loaded via a namespace (and not attached): [1] compiler_3.6.0 grid_3.6.0 lattice_0.20-38 ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
