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Bug or Feature in find()?
Posted:
Dec 7, 1996 11:40 AM
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I'm using MATLAB 4.2c dated Dec 31 1994 on a SunOS 4.x machine.
If I use find with zero (or one) output parameter(s) on a full
vector, the answer will be in the same row-or-column orientation as
the input:
>> a = rand(4);
>> find(a(1,:))
ans =
1 2 3 4
>> find(a(:,1))
ans =
1
2
3
4
but if I use it on a sparse row or column vector, the answer will
always be a column vector:
>> a = sparse(a);
>> find(a(1,:))
ans =
1
2
3
4
>> find(a(:,1))
ans =
1
2
3
4
This not only cost me a small but annoying amount of time trying to
figure out why my nifty slick "pull out the innermost loop with
vectorization" trick was failing, but also cost the MathWorks a
little bit of free advertising, as the professor who was watching me
try to prove how much easier it is to code numerical stuff in MATLAB
than in C remained unimpressed.
--JMike
-------------------------------------------
J Michael Hammond <hammond@cs.utk.edu> |
Univ of Tenn Dept of Comp Sci |
http://www.cs.utk.edu/~hammond/jmike.html |
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