[R] proportional matrix rows

[Robin Hankin]

Hi

I have a two-column integer matrix like this:


R> jj

       [,1] [,2]
  [1,]   -1    1
  [2,]   -2    2
  [3,]   -7    6
  [4,]   -8    7
  [5,]   -6    5
  [6,]   -9    8
  [7,]   -5    4
  [8,]    3   -3
  [9,]  -10    9
[10,]   -4    3

I want a diagnostic that detects whether a row is a multiple of
the first row or not.  In this case, this would be rows 1,2, and 8.

How to do this nicely?  Sometimes the first row has a zero, so the
method would have to work on

      [,1] [,2]
[1,]    0    1
[2,]    1    1
[3,]    0    8
[4,]    0   -4
[5,]    0    0
[6,]    4    0
 >

in which case rows 1,3,4,5 are multiples.  It'd be nice to have
a solution that works for any number of columns.

--
Robin Hankin
Uncertainty Analyst
Southampton Oceanography Centre
European Way, Southampton SO14 3ZH, UK
  tel  023-8059-7743