I think what I would call a "row" is different than what you are calling a
row. I would call the third row
"ten", "eleven", "twelve"
but that wouldn't be too difficult, so I assume that you mean
"three"
"six"
"nine"
"twelve"
for this, I'd do something like this
@row3 = map {[splice(@$_, 3, 1)]} @matrix;
now, @matrix looks like this
(
["one","two"]
["four","five"]
["seven","eight"]
["ten","eleven"]
)
and @row three looks like this
(
["three"]
["six"]
["nine"]
["twelve"]
)
Note: @row3 three is still a list of lists. If you want it in a regular
list format, remove the square brackets.
HTH
wantor
> -----Original Message-----
> From: Moulder, Glen [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, March 13, 2001 2:46 PM
> To: 'perl-win32-users'
> 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
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