On 10/22/2012 1:10 PM, CMB123 wrote:
Hi all,
I'm working with a large data set (on the order of 300X300) and trying to
apply a function which compares the elements of all possible 2x2
submatrices. There are rc(r-1)(c-1) such submatrices, so obviously the naive
method of looping through the rows
Inline.
On Mon, Oct 22, 2012 at 1:10 PM, CMB123 wrote:
> I apologize if the term "submatrix" was confusing - I am basically 2 rows and
> 2 columns from a r x c matrix to construct 2x2 matricies. Thus, the
> choose(r,2) * choose(c,2) possible combinations.
>
> For each matrix [(a,b), (c,d)],
What
I apologize if the term "submatrix" was confusing - I am basically 2 rows and
2 columns from a r x c matrix to construct 2x2 matricies. Thus, the
choose(r,2) * choose(c,2) possible combinations.
For each matrix [(a,b), (c,d)], I am testing a > b, b > d, d > c, and c > a.
For the sake of simplicity
Hello,
If your matrix is in the order of 300x300, the problem of extracting all
possible submatrices and applying a function will allways be a large
one, but the use of ?combn may reduce it a bit if the order of
rows/columns in the submatrices doesn't matter. It can reduce it from
300^4 = 8.1
300x300 isn't terribly large; looping should work just fine. But I'm
confused about a 2x2 submatrix:
I would have thought that a submatrix would be adjacent elements, like
x[1:2, 1:2]
or
x[13:14, 296:297]
but your loop compares all possible sets of four elements, so the
matrix position doesn't matt
Hi all,
I'm working with a large data set (on the order of 300X300) and trying to
apply a function which compares the elements of all possible 2x2
submatrices. There are rc(r-1)(c-1) such submatrices, so obviously the naive
method of looping through the rows and columns is computationally unfeasib
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