Hi Peter, Gabor
On Feb 7, 2005, at 04:42 pm, Peter Dalgaard wrote:
Gabor Grothendieck <[EMAIL PROTECTED]> writes:
Robin Hankin <r.hankin <at> soc.soton.ac.uk> writes:
: I want a diagnostic that detects whether a row is a multiple of : the first row or not.
..and in that case it might be easier just to calculate the dot product with the orthogonal of mat[1,]:
z <- jj[1,] jj %*% c(z[1], -z[2])[,1] [1,] 0 [2,] 0 [3,] 1 [4,] 1 [5,] 1 [6,] 1 [7,] 1 [8,] 0 [9,] 1 [10,] 1
(Notice that the value "1" just comes from Robin being singularly bad at selecting "arbitrary" rows that are not proportional to the first one!)
Heh. I spent some considerable time pondering this and realized that if one
views jj as a bunch of two-by two matrices jj[c(a,b),] then in my application,
many of these matrices are either singular or unimodular (that is, a matrix with a
determinant of one).
Your insight above is is VERY VERY helpful
Thank you.
-- Robin Hankin Uncertainty Analyst Southampton Oceanography Centre European Way, Southampton SO14 3ZH, UK tel 023-8059-7743
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