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From: Walter Roberson on 12 May 2010 13:27
EE Student wrote:
> "someone" <someone(a)somewhere.net> wrote in message
> <hseia9$3t$1(a)fred.mathworks.com>...
>> "EE Student " <np7(a)cec.wustl.edu> wrote in message
>> <hsei0s$aoi$1(a)fred.mathworks.com>...
>> > "Dimitris Valapetrou" <diastro(a)email.com> wrote in message
>> <hseg14$1jn$1(a)fred.mathworks.com>...
>> > > How can i calculate the first three maximum values of a signal

> True, I guess i didnt see the way to implement it with max short of
> writting it into a recursion or something similar (which seems to be
> what you suggested) and thought that would be overkill as opposed to
> just sorting.

Keep in mind that algorithmic "average case" "order" for sort() is
N*log(N) (where N is the number of elements in the vector), but that the
algorithmic order for M passes of "max" is M*N. The further that M is
from log(N), the more efficient relatively doing M scans over the matrix
will be. exp(3) is roughly 10, so for more than 10 or so elements, using
max() three times would be faster than sort().
From: someone on 12 May 2010 13:34
Walter Roberson <roberson(a)hushmail.com> wrote in message <dyBGn.6314$HG1.1266(a)newsfe21.iad>...
> EE Student wrote:
> > "someone" <someone(a)somewhere.net> wrote in message
> > <hseia9$3t$1(a)fred.mathworks.com>...
> >> "EE Student " <np7(a)cec.wustl.edu> wrote in message
> >> <hsei0s$aoi$1(a)fred.mathworks.com>...
> >> > "Dimitris Valapetrou" <diastro(a)email.com> wrote in message
> >> <hseg14$1jn$1(a)fred.mathworks.com>...
> >> > > How can i calculate the first three maximum values of a signal
>
> > True, I guess i didnt see the way to implement it with max short of
> > writting it into a recursion or something similar (which seems to be
> > what you suggested) and thought that would be overkill as opposed to
> > just sorting.
>
> Keep in mind that algorithmic "average case" "order" for sort() is
> N*log(N) (where N is the number of elements in the vector), but that the
> algorithmic order for M passes of "max" is M*N. The further that M is
> from log(N), the more efficient relatively doing M scans over the matrix
> will be. exp(3) is roughly 10, so for more than 10 or so elements, using
> max() three times would be faster than sort().

Thanks for the insight Walter. You learn something new everyday.
I would have guessed more like thousands rather than tens.
From: Dimitris Valapetrou on 15 May 2010 14:09
"Dimitris Valapetrou" <diastro(a)email.com> wrote in message <hseg14$1jn$1(a)fred.mathworks.com>...
> How can i calculate the first three maximum values of a signal using the max fuction?
>
> thanks for your help!

Thanks a lot guys!
Your replies really helped me out.
i finally used the sort() function as the most efficient.
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