Re: fastest way to test a logical vector

[Jaroslav Hajek]

On Wed, Jan 20, 2010 at 6:20 PM, Dupuis <address@hidden> wrote:
>
>
> Carlo de Falco-2 wrote:
>>
>>
>>
>>> Regards
>>>
>>> Pascal
>>
>> you could use
>>
>> numel (find (x(indi-(1:4)))) >= 2
>>
>> c.
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>>
>>
>
> Hello,
> I tried to implement most of the logic I needed in the simple, enclosed
> file. The results clearly show that replacing 'for' loops by direct work on
> vectors is way faster.
> http://old.nabble.com/file/p27245361/speedtest.m speedtest.m
>

Yes, this is quite expectable.

> Now my problem is that I'm implementing a kind of state machine. I can write
> state(2) as a function of state(1) and so on, but state(1) depends on the
> latest state, so direct work on vector would not work. Any idea on how to
> solve this ?

This kind of problems is quite difficult to vectorize, admittedly. It
heavily depends on the problem at hand. In general, the "filter"
function can be of use (for difference equations), as well as the
cumulative reductions (cumsum etc).
For other options, see the signal package:
http://octave.sourceforge.net/signal/index.html

-- 
RNDr. Jaroslav Hajek, PhD
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz