Convertion between empty matrix and Null
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I am trying to check if two vectors are identical, quite often these can be null or empty and of different lengths. I confess my ignorance as to the processes which decide wheather the matrix is null or empty, but I am trying to use an all command (the vectors are sorted and have unique elements). I hit a bug when one vector is null and the other Empty. Any ideas?
{strato =
[]
>> stratn
stratn =
Empty matrix: 1-by-0
>> stratn==stratn
ans =
Empty matrix: 1-by-0
K>> all(stratn==stratn)
ans =
1
K>> all(strato==strato)
ans =
1
K>> all(strato==stratn) ??? Error using ==> eq Matrix dimensions must agree.}
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Jacob Halbrooks
le 9 Mar 2012
It is informative to inspect the dimensions of []:
>> size([])
ans =
0 0
In equality checks, the dimensions must agree, so this will be unequal to "vector" empties:
>> isequal(ones(0,0), ones(0,1))
ans =
0
I would suggest you use ISEMPTY if you want to treat all empties as the same:
>> isequal(isempty(ones(0,0)), isempty(ones(0,1)))
ans =
1
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Walter Roberson
le 9 Mar 2012
A matrix is empty if any of its dimensions are 0.
See also isempty()
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