Unexpected behaviour of base::qr()$rank

On 22.06.2017 17:11, Bernd Funovits wrote:

Hello,

I experienced some unexpected behaviour while determining the rank of matrices (sometimes 1x1 matrices):
base::qr(matrix(1e-20))$rank returns 1 (incorrect)
base::qr(diag(c(1, 1e-20)))$rank returns 2 (incorrect)

Why do you believe this is incorrect?

0 != 1e-20

and 1e-20 is well representable without significant rounding errors given

.Machine$double.xmin

[1] 2.225074e-308


Best,
Uwe Ligges