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Re: Empty matrices don't have trailing ones?
From: |
Ben Abbott |
Subject: |
Re: Empty matrices don't have trailing ones? |
Date: |
Thu, 10 May 2012 07:43:23 -0400 |
On May 10, 2012, at 12:46 AM, Jordi Gutiérrez Hermoso wrote:
> I'm trying to figure out the rationale for having dim_vector::redim
> padding all-zero dim_vectors with zeros instead of ones. This results
> in surprising behaviour like some empty matrices getting their
> trailing dimensions being zero instead of one, so this errors out:
>
> x = zeros (0, 0);
> x(:,:,1)
>
> I don't think it should (and neither does Matlab, I'm told).
Not sure if you had any doubts about Matlab ...
x = zeros(0,0);
x(:,:,1)
ans =
[]
> Note that
> this is a peculiarity of trailing dimensions being zero instead of the
> usual singletons.These two are fine, because dim_vector::redim doesn't
> pad them with zeros:
>
> x = zeros (1, 0, 0);
> x(1,:,:)
> x(1,:,:,1)
x = zeros(1,0,0);
x(:,:,1)
Index exceeds matrix dimensions.
x(1,:,:)
ans =
Empty array: 1-by-0-by-0
x(1,:,:,1)
ans =
Empty array: 1-by-0-by-0
Ben