# NAME

Statistics::Basic::Covariance - find the covariance between two lists

# SYNOPSIS

Invoke it this way:

``    my \$covariance = covariance( [1,2,3], [1,2,3] );``

Or this way:

``````    my \$v1  = vector(1,2,3);
my \$v2  = vector(1,2,3);
my \$cov = cov(\$v1,\$v2);``````

And then either query the values or print them like so:

``````    print "The covariance between \$v1 and \$v2: \$covariance\n";
my \$cq = \$cov->query;
my \$c0 = 0+\$cov;``````

Create a 20 point "moving" covariance like so:

``````    use Statistics::Basic qw(:all nofill);

my \$sth = \$dbh->prepare("select col1,col2 from data where something");
my \$len = 20;
my \$cov = cov();
\$cov->set_size(\$len);

\$sth->execute or die \$dbh->errstr;
\$sth->bind_columns( my (\$lhs, \$rhs) ) or die \$dbh->errstr;

my \$count = \$len;
while( \$sth->fetch ) {
\$cov->insert( \$lhs, \$rhs );
if( defined( my \$c = \$cov->query ) ) {
print "Covariance: \$c\n";
}

# This would also work:
# print "Covariance: \$cov\n" if \$cov->query_filled;
}``````

# METHODS

This list of methods skips the methods inherited from Statistics::Basic::_TwoVectorBase (things like query(), insert(), and ginsert()).

new()

Create a new Statistics::Basic::Covariance object. This function takes two arguments -- which can either be arrayrefs or Statistics::Basic::Vector objects. This function is called when the covariance() shortcut-function is called.

query_vector1()

Return the Statistics::Basic::Vector for the first vector.

query_vector2()

Return the Statistics::Basic::Vector object for the second vector.

query_mean1()

Returns the Statistics::Basic::Mean object for the first vector.

query_mean2()

Returns the Statistics::Basic::Mean object for the second vector.

Paul Miller `<jettero@cpan.org>`