Gunurath, one last thougth, for the variance you should divide the
number of observations before taking the square root.
You may also have a look at the stats function, that you could use over
the diagonal.
Louis
Op woensdag 30-05-2012 om 14:20 uur [tijdzone +0200], schreef louis:
> Hi Gurunath,
>
> Maybe I can help with the problem. I am not an expert at PDL either, but
> here is how I would do it. I am supposing you have square matrices.
>
> Suppose you have some pdl like below.
>
> my $a = pdl([2,2,2],[3,1,0],[2,5,1]);
>
> To find the diagonal you can use diagonal(0,1), where the arguments are
> the dimensions to take the diagonal over.
>
> my $b =$a ->diagonal(0,1);
> print ("$a, $b\n");
>
> Here is how you can take a sum of the diagonal
>
> print (sumover($b),"\n");
>
> Then you find the number of elements, assuming your matrices are square
> you can take either of the two dimension, or otherwise use the nelem
> function on the diagonal.
>
> print ($b->dim(0),"\n");
>
> You can do that in one step
>
> print (sumover($a->diagonal(0,1))/$a->dim(0),"\n");
>
> As for the standardeviation. You can calculate the variance as the
> internal product of the diagonal minus the average.
>
> my $b =- sumover($b)/$b->dim(0);
> print ($b x transpose($b) );
>
> I will leave you take the square root of that with sqrt();
>
> Hope it helps, maybe somebody knows a faster way.
>
> Regards, LouisOp zaterdag 26-05-2012 om 12:09 uur [tijdzone +0530],
> schreef Gurunath Katagi:
>
> > Dear all,
> > I am new to using pdl ...
> >
> > i have some 30000 matrix from which i want to extract the diagonal
> > elements from each of them and get the average and standard deviation
> > of each of the diagonal elements among 30000 matrix.
> >
> > however, i am able to able to this in MATLAB, but its very slow ...
> >
> > Can anybody help to write this is program using pdl and is there
> > anyway that i can process it fast using pdl ...
> >
> > my program goes like this :
> > read the matrix files
> > extract the diagnol elements from each of the them
> > and find the avg. and std.
> >
> > I tried it, but i am facing problem with respect to extracting the
> > diagonal elements...
> >
> >
> > Thank you
> > Gurunath
> >
> >
> >
> >
> >
> >
> >
> >
> > _______________________________________________
> > Perldl mailing list
> > [email protected]
> > http://mailman.jach.hawaii.edu/mailman/listinfo/perldl
>
>
>
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