----- Original Message -----
From: Moulder, Glen <[EMAIL PROTECTED]>
To: 'perl-win32-users' <[EMAIL PROTECTED]>
Sent: Wednesday, March 14, 2001 7:46 AM
Subject: Q: Using splice on a matrix
> Good day perlfolk,
>
> I often work with data matrices (lists of lists) in my scripts. A simple
example is:
>
> @matrix = ();
> @list1 = ("one","two","three");
> @list2 = ("four","five","six");
> @list3 = ("seven","eight","nine");
> @list4 = ("ten","eleven","twelve");
> push @matrix, [ @list1 ];
> push @matrix, [ @list2 ];
> push @matrix, [ @list3 ];
> push @matrix, [ @list4 ];
>
> Sometimes I want to extract one row, like maybe the third one, shortening
the matrix and putting the row in another list. The only method I've found
so far that works is the tedious one of using for loops to iterate through
the matrix and create two new matrices, one that contains the row(s) I want,
and one the row(s) I don't currently want, discarding the original matrix.
I've tried using different variations of splice (sample below) to accomplish
the creation of the "wanted" and "unwanted" matrices, but have had no
success.
>
> $row_elements = $#list4;
> splice(@new_list,0,$row_elements,splice(@matrix,2,$row_elements));
>
> None of the common Perl books talk about this. Chapter 7 of Mastering
Algorithms with Perl talks about two modules for dealing with matrices,
Math::MatrixReal and PDL. PDL is only available on CPAN and does not
install correctly on Win32. The other module has an unusual one-indexing
feature (the upper left element of a matrix is 1,1 - not 0,0 as in regular
lists) that I don't want to use because I'm sure I'll get confused working
with indices on different types of lists. Plus, I'd rather not install yet
another module to do something that could be accomplished with a function.
Anyone working with matrices and splice? I could use a hand understanding
this.
>
> TIA,
> Glen
I think you'll find this covered in the perllol manpage.
perldoc -m perllol
Cheers,
Rob
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