Re: C++ template

[Henry F. Mollet]

I have an older version of octave (2.1.46) and I get
octave:2> a(6)==a(1,2)
error: single index only valid for row or column vector
error: evaluating binary operator `==' near line 2, column 5

I have to vectorize 'a' first before I can compare a(6) with a(1,2):
octave:2> b=vec(a);
octave:5> b(6)==a(1,2)
ans = 1

Will a newer version of Octave know what to do with a(6) if a is a 5x5
matrix?
Henry



on 10/4/04 5:12 AM, Stefan van der Walt at address@hidden wrote:

> I am not sure what you mean, since all the examples listed under "Linear
> Indexing" in the document below works as stated.
> 
> octave:1> a = ones(5,5)
> a =
> 
> 1  1  1  1  1
> 1  1  1  1  1
> 1  1  1  1  1
> 1  1  1  1  1
> 1  1  1  1  1
> 
> octave:2> a(6)==a(1,2)
> ans = 1
> 
> Which compares the 6th element of 'a' to the second in the first row.
> If you want to compare a(6) to the first two elements, you have to do
> 
> octave:6> a(6)==a(1:2)
> 
> or 
> 
> octave:7> a(6)==a([1 2])
> 
> Regards
> Stefan
> 
> On Mon, Oct 04, 2004 at 04:46:22AM -0500, Fredrik Bulow wrote:
>> hmm....
>> 
>> Linear indexing (i.e. a(6)==a(1,2) for a 5x5 matrix) does not seem to be
>> implemented yet. Or can it be turned on in some way? (Linear indexing is
>> described in the below link.)
>> 
>> The "find" function seems to be built on the idea that linear indexing
>> is available since find(eye(5)) does return [1 7 13 19 25]'.
>> 
>> /Fredrik
>> 
>> On Mon, 2004-10-04 at 07:19, Paul Thomas wrote:
>>> Fredrik Bulow wrote:
>>> 
>>>> Thank you!
>>>>  
>>>> 
>>> You are more than welcome.
>>> 
>>>>  
>>>> 
>>> Most octave programmes can be vectorised, although it is not always
>>> obvious how.  All that applies to Matlab, in this area, applies to
>>> octave as well.  The following technical note is therefore very useful
>>> and should be read by all octave/Matlab/Scilab/... users, regardless of
>>> which they use:
>>> 
>>> http://www.mathworks.com/support/tech-notes/1100/1109.html
>>> 
>>> The speedup that can be obtained is often more than that from writing a
>>> dynamically linked function - especially if the development time of the
>>> latter is taken into account.
>>> 
>>> Best regards
>>> 
>>> Paul T
>>> 
>> 
>> 
>> 
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> 
> 
> 
> -------------------------------------------------------------
> Octave is freely available under the terms of the GNU GPL.
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-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
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