Re: Matrix annotation?


"David C. Ullrich" <dullrich@xxxxxxxxxxx> wrote in message
news:5bl664luhbmibccpnq7ft3vkbm9rp91tqg@xxxxxxxxxx
On Wed, 25 Jun 2008 15:23:27 -0700 (PDT), onofftopic@xxxxxxxxx wrote:

Hi,

for instance each element of mXn matrix A is annotated as a_i,j.

However, is it "mathematically allowed" to annotate each element of
matrix A as a_i,j and to write/say that this matrix has a dimension
i'Xj'; i.e. may i use i' and j' as symbols for dimension of matrix?

No. Say A is 2x2 and you say A is i x j. That says i =2 and j = 2.
And now that i and j are fixed you can't refer to the general
entry in the matrix as a_i,j anymore; a_i,j means a_2,2.


Well, i didnt write it clearly, but i would say A is i' x j', i.e. i would
use i' and j' for dimension annotation:

i'=2
j'=2

and i, j for elements annotation:

i=1,2
j=1,2

Is this kind of annotation "allowed"?


.