[Rd] wrong matrix dimension in sparseQR

Serguei Sokol sokol at insa-toulouse.fr
Thu Jan 18 16:13:43 CET 2018


I came across a case when the dimensions of matrices returned by qr()
operated on a sparse matrix does not coincide with the initial matrix.

Here is a spinet code that should produce an example (one of many that I could provide):

  a=matrix(rnorm(m*n), m, n)
  a[sample(seq(m*n), m*(n-4))]=0
  a=as(a, "Matrix")
  stopifnot(nrow(qa at R) == m)
  # On my box I have nrow(qa at R):=207 while should be 205 as m is)

Note that for m=203 and n=197, the same code produce right (i.e. coinciding) dimensions.

Have I missed something?


 > R.version
platform       x86_64-pc-linux-gnu
arch           x86_64
os             linux-gnu
system         x86_64, linux-gnu
major          3
minor          4.3
year           2017
month          11
day            30
svn rev        73796
language       R
version.string R version 3.4.3 (2017-11-30)
nickname       Kite-Eating Tree

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