Math::...Vector(3pm)

💖 Math::SparseVector 💖

okay so bestie, welcome to the manual page for Math::SparseVector, straight out of the Perl User Contributed Documentation 💅. If you've ever wanted a vector that only bothers to remember the stuff that isn't zero, this is the moment. She does setting a value in a vector, reading a value at a given index, obtaining all indices, addition and dot product of two sparse vectors, and vector normalization. iconic behavior, no cap 🎀

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🌈 MODULE HISTORY 🌈

so like, this module is the successor to Sparse::Vector — it got re-cast into this shiny new namespace so that another module, Math::SparseMatrix, could exist and make use of it. glow-up era fr fr ✨

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🦋 SYNOPSIS 🦋

use Math::SparseVector;

# creating an empty sparse vector object
$spvec=Math::SparseVector->new;

# sets the value at index 12 to 5
$spvec->set(12,5);

# returns value at index 12
$value = $spvec->get(12);

# returns the indices of non-zero values in sorted order
@indices = $spvec->keys;

# returns 1 if the vector is empty and has no keys
if($spvec->isnull) {
  print "vector is null.\n";
}
else  {
  print "vector is not null.\n";
}

# print sparse vector to stdout
$spvec->print;

# returns the string form of sparse vector
# same as print except the string is returned
# rather than displaying on stdout
$spvec->stringify;

# adds sparse vectors v1, v2 and stores
# result into v1
$v1->add($v2);

# adds binary equivalent of v2 to v1
$v1->binadd($v2);
# binary equivalnet treats all non-zero values
# as 1s

# increments the value at index 12
$spvec->incr(12);

# divides each vector entry by a given divisor 4
$spvec->div(4);

# returns norm of the vector
$spvec_norm = $spvec->norm;

# normalizes a sparse vector
$spvec->normalize;

# returns dot product of the 2 vectors
$dotprod = $v1->dot($v2);

# deallocates all entries
$spvec->free;

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🌸 USAGE NOTES 🌸

1. Loading Math::SparseVector Module

to even touch this module you gotta slide this line into your Perl program before you use any of the supported methods:

use Math::SparseVector;

2. Creating a Math::SparseVector Object

this next line creates a brand new object of the Math::SparseVector class, and we're gonna refer to her as 'spvec':

$spvec=Math::SparseVector->new;

and when she's born, 'spvec' is initially empty. a clean slate, a blank canvas, main character energy 🫶

3. Using Methods

now you can run any of these methods on your 'spvec' Math::SparseVector object. let's gooo 👑

1. set(i,n) — Sets the value at index i to n

# equivalent to $spvec{12}=5;
$spvec->set(12,5);

2. get(i) — Returns the value at index i

# equivalent to $value=$spvec{12};
$value = $spvec->get(12);

3. keys() — Returns the indices of all non-zero values in the vector

# equivalent to @keys=sort {$a <=> $b} keys %spvec;
@indices = $spvec->keys;

4. isnull() — Returns 1 if the vector is empty and has no keys

# similar to
# if(scalar(keys %spvec)==0) {print "vector is null.\n";}
if($spvec->isnull) { print "vector is null.\n"; }

5. print() — Prints the sparse vector to stdout

output will show a list of space separated 'index value' pairs for each non-zero 'value' in the vector.

# similar to
# foreach $ind (sort {$a<=>$b} keys %spvec)
    # { print "$ind " . $spvec{$ind} . " "; }
$spvec->print;

6. stringify() — Returns the vector in a string form

same as the print() method except the vector is written to a string that gets returned instead of being displayed onto stdout.

# the below will do exactly same as $spvec->print;
$string=$spvec->stringify;
print "$string\n";

7. v1->add(v2) — Adds contents of v2 to vector v1

similar to v1+=v2

$v1->add($v2);

if v1 = (2, , , 5, 8, , , , 1) & v2 = ( , 1, , 3, , , 5, , 9)

where blanks show the 0 values that are not stored in Math::SparseVector.

then after $v1->add($v2);:

v1 = (2, 1, , 8, 8, , 5, , 10) and v2 remains same 😌

8. v1->binadd(v2) — Binary equivalent of v2 is added into v1

the binary equivalent of a vector is obtained by setting all non-zero values to 1s.

if v1 = (1, , , 1, 1, , , , 1) & v2 = ( , 1, , 1, , , 1, , 1)

then, after v1->binadd(v2), v1 will be (1, 1, , 1, 1, , 1, , 1).

if v1 = (1, , , 1, 1, , , , 1) & v2 = ( , 1, , 3, , , 5, , 9)

v1->binadd(v2); will set v1 to (1, 1, , 1, 1, , 1, , 1).

9. incr(i) — Increments the value at index i

# is similar to $spvec{12}++;
$spvec->incr(12);

10. div(n) — Divides each vector entry by a given divisor n

$spvec->div(4);

if spvec = (2, , , 5, 8, , , , 1) then $spvec->div(4) will set spvec to (0.5, , , 1.25, 2, , , , 0.25)

11. norm() — Returns the norm of a given vector

$spvec_norm = $spvec->norm;

if spvec = (2, , , 5, 8, , , , 1) $spvec->norm will return the value

= sqrt(2^2 + 5^2 + 8^2 + 1)
= sqrt(4 + 25 + 64 + 1)
= 9.69536

12. v1->dot(v2) — Returns the dot product of two vectors

$dotprod = $v1->dot($v2);

if v1 = (2, , , 5, 8, , , , 1) & v2 = ( , 1, , 3, , , 5, , 9)

v1->dot(v2) returns

5*3 + 1*9 = 15 + 9 = 24

13. free() — Deallocates all entries and makes the vector empty

$spvec->free;

will set spvec to null vector ()

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👑 AUTHORS 👑

• Amruta Purandare, University of Pittsburgh — amruta at cs.pitt.edu
• Ted Pedersen, University of Minnesota, Duluth — tpederse at d.umn.edu
• Mahesh Joshi, Carnegie-Mellon University — maheshj at cmu.edu

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📜 COPYRIGHT AND LICENSE 📜

Copyright (c) 2006-2008, Amruta Purandare, Ted Pedersen, Mahesh Joshi

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to

 The Free Software Foundation, Inc.,
 59 Temple Place - Suite 330,
 Boston, MA  02111-1307, USA.

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⚠️ okay real talk bestie, that "WITHOUT ANY WARRANTY" thing is not a vibe, it's the actual legal text — no promises of merchantability, no promises of fitness for a particular purpose. read the GPL for the full tea 🍓

and that's the whole page, mwah 💋 this was Math::SparseVector for perl v5.26.1, dated 2018-03-30, served fresh from the Perl User Contributed Documentation. go build something cute with your sparse vectors, you ate 💅✨