Re: [eigen] first time usage by me! and very satisfied!

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thank you Andre.

indeed I though it would not harm to add shortcuts for most common
statistic reduction methods. they would be added in the Array module,
and also be available in a column and row wise flavors. just one
thing: actually the stddev and variance need to first compute the mean
and I guess that often you want both, so I suggest to have 2 versions
of stddev and variance like this:

/* use the precomputed mean to compute the stddev */
Scalar stddev(const Scalar& mean) const;
/* shortcut */
Scalar stddev() const { return stddev(mean()); }

maybe we can even have a single version with a default arg value:
Scalar stddev(const Scalar& _mean = mean()) const;
but I don't know if it's legal to call a non static member function on *this...

I prefer that to something like:
Scalar stddev(Scalar*  returnedMean = 0) const;
because in case you have already computed the mean value you cannot
tell stddev to use it...

so to summarize we would add:

* mean()

* standardDeviation([precomputed_mean])
yeah, eventually "standardDeviation" is not too long

* variance([precomputed_mean])

* median()
maybe here we could have an optional argument to tell if the vector is
already sorted ??

* sort()
median needs a sort algo, and here I really mean "sort", not "sorted",
so it an in-place sort


On Thu, Sep 11, 2008 at 8:29 PM, Andre Krause <post@xxxxxxxxxxxxxxxx> wrote:
> dear list, just wanted to let you all know i am using eigen2 alpha 07 for the
> first time - and i am very satisfied. works like charm, with no problems on
> win32 and visualc++ 2008.
> though i am missing some basic convenience functions like mean, medium, stdev
> etc. . i already heard on #eigen, that they are planned for some future release.
> kind regards,
>        andre

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