PDL is of course in progress, but it is somewhat mature by now, being
over 10 years old... :-)
PDL::Matrix is a "convenience" interface to PDL itself -- all it does
is invert the row/column order. PDLs are normally stored in
(column,row) order following computational convention rather than
(row,column) as mathematicians prefer. Rather than decipher which
methods have been subclassed and which have not, I always use PDLs
themselves -- that way at least the (column,row)
order is consistent.
Then you can use dims() rather than mdims().
Inner product of two PDLS $a and $b is
($a * $b)->sumover
if you want to collapse columns, or
($a * $b)->mv(1,0)->sumover
if you want to collapse rows.
There is an introductory book ion the PDL language that has some
tricks and such in it. You can download it from Sourceforge -- it is
in a separate cvs repository.
As for getting your matrices back out of PDLS: are you trying to
export them to a file [ try rcols() or rfits() ]? Or to another Perl
application [ try list() ]? Or perhaps to a C module that called PDL
via the perlapi? There are many I/O techniques, depending on what
you want to do.
Cheers,
Craig
On Dec 19, 2006, at 8:39 AM, laurent exsteens wrote:
hello,
I'm a little confuse with PDL::Matrix...
Is the code in "Work in Progress"? I see in the PDL manpages (on
the web site) that not all the operators are redefined...
Here is my problem: I have to use SVD to compress a quite huge
matrix (~5000 columns), so I'm using SVD on R, but I want to
implement this in my perl interface. What I want is to pass my
matrix and get back another matrix (not a piddle) but:
I do not understand how the matrix is saved: by columns (I suppose)
or by lines, still mdims seems to not work... ("" print
$datasAdjust->mdims() "" don't write anything on the terminal...)
I don't know how to scale the matrix (centering is sufficiant, no
need to realy scale)
I don't know how to make an inner product (The manpages say that
they is not yet...)
I don't know how to manipulate the matrix by hand or to get the
informations back to my own format (not a piddle)
So, is this package usable, or I have to find another way (perhaps
use the GSL library whith binding from perl...?)
If it is usable, where can I get some tutorial or documentation
other than the manpages that give me the tricks I need?
regards,
Laurent.
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