Provided by: libmath-utils-perl_1.14-2_all bug

NAME

       Math::Utils - Useful mathematical functions not in Perl.

SYNOPSIS

           use Math::Utils qw(:utility);    # Useful functions

           #
           # Base 10 and base 2 logarithms.
           #
           $scale = log10($pagewidth);
           $bits = log2(1/$probability);

           #
           # Two uses of sign().
           #
           $d = sign($z - $w);

           @ternaries = sign(@coefficients);

           #
           # Using copysign(), $dist will be doubled negative or
           # positive $offest, depending upon whether ($from - $to)
           # is positive or negative.
           #
           my $dist = copysign(2 * $offset, $from - $to);

           #
           # Change increment direction if goal is negative.
           #
           $incr = flipsign($incr, $goal);

           #
           # floor() and ceil() functions.
           #
           $point = floor($goal);
           $limit = ceil($goal);

           #
           # gcd() and lcm() functions.
           #
           $divisor = gcd(@multipliers);
           $numerator = lcm(@multipliers);

           #
           # Safer summation.
           #
           $tot = fsum(@inputs);

           #
           # The remainders of n after successive divisions of b, or
           # remainders after a set of divisions.
           #
           @rems = moduli($n, $b);

       or

           use Math::Utils qw(:compare);    # Make comparison functions with tolerance.

           #
           # Floating point comparison function.
           #
           my $fltcmp = generate_fltmcp(1.0e-7);

           if (&$fltcmp($x0, $x1) < 0)
           {
               add_left($data);
           }
           else
           {
               add_right($data);
           }

           #
           # Or we can create single-operation comparison functions.
           #
           # Here we are only interested in the greater than and less than
           # comparison functions.
           #
           my(undef, undef,
               $approx_gt, undef, $approx_lt) = generate_relational(1.5e-5);

       or

           use Math::Utils qw(:polynomial);    # Basic polynomial ops

           #
           # Coefficient lists run from 0th degree upward, left to right.
           #
           my @c1 = (1, 3, 5, 7, 11, 13, 17, 19);
           my @c2 = (1, 3, 1, 7);
           my @c3 = (1, -1, 1)

           my $c_ref = pl_mult(\@c1, \@c2);
           $c_ref = pl_add($c_ref, \@c3);

EXPORT

       All functions can be exported by name, or by using the tag that they're grouped under.

   utility tag
       Useful, general-purpose functions, including those that originated in FORTRAN and were
       implemented in Perl in the module Math::Fortran, by J. A. R. Williams.

       There is a name change -- copysign() was known as sign() in Math::Fortran.

       log10()

           $xlog10 = log10($x);
           @xlog10 = log10(@x);

       Return the log base ten of the argument. A list form of the function is also provided.

       log2()

           $xlog2 = log2($x);
           @xlog2 = log2(@x);

       Return the log base two of the argument. A list form of the function is also provided.

       sign()

           $s = sign($x);
           @valsigns = sign(@values);

       Returns -1 if the argument is negative, 0 if the argument is zero, and 1 if the argument
       is positive.

       In list form it applies the same operation to each member of the list.

       copysign()

           $ms = copysign($m, $n);
           $s = copysign($x);

       Take the sign of the second argument and apply it to the first. Zero is considered part of
       the positive signs.

           copysign(-5, 0);  # Returns 5.
           copysign(-5, 7);  # Returns 5.
           copysign(-5, -7); # Returns -5.
           copysign(5, -7);  # Returns -5.

       If there is only one argument, return -1 if the argument is negative, otherwise return 1.
       For example, copysign(1, -4) and copysign(-4) both return -1.

       flipsign()

           $ms = flipsign($m, $n);

       Multiply the signs of the arguments and apply it to the first. As with copysign(), zero is
       considered part of the positive signs.

       Effectively this means change the sign of the first argument if the second argument is
       negative.

           flipsign(-5, 0);  # Returns -5.
           flipsign(-5, 7);  # Returns -5.
           flipsign(-5, -7); # Returns 5.
           flipsign(5, -7);  # Returns -5.

       If for some reason flipsign() is called with a single argument, that argument is returned
       unchanged.

       floor()

           $b = floor($a/2);

           @ilist = floor(@numbers);

       Returns the greatest integer less than or equal to its argument.  A list form of the
       function also exists.

           floor(1.5, 1.87, 1);        # Returns (1, 1, 1)
           floor(-1.5, -1.87, -1);     # Returns (-2, -2, -1)

       ceil()

           $b = ceil($a/2);

           @ilist = ceil(@numbers);

       Returns the lowest integer greater than or equal to its argument.  A list form of the
       function also exists.

           ceil(1.5, 1.87, 1);        # Returns (2, 2, 1)
           ceil(-1.5, -1.87, -1);     # Returns (-1, -1, -1)

       fsum()

       Return a sum of the values in the list, done in a manner to avoid rounding and
       cancellation errors. Currently this is done via Kahan's summation algorithm
       <https://en.wikipedia.org/wiki/Kahan_summation_algorithm>.

       softmax()

       Return a list of values as probabilities.

       The function takes the list, and creates a new list by raising e to each value. The
       function then returns each value divided by the sum of the list. Each value in the new
       list is now a set of probabilities that sum to 1.0.

       The summation is performed using fsum() above.

       See Softmax function <https://en.wikipedia.org/wiki/Softmax_function> at Wikipedia.

       uniform_scaling

       uniform_01scaling

       Uniformly, or linearly, scale a number either from one range to another range
       ("uniform_scaling()"), or to a default range of [0 .. 1] ("uniform_01scaling()").

           @v = uniform_scaling(\@original_range, \@new_range, @oldvalues);

       For example, these two lines are equivalent, and both return 0:

           $y = uniform_scaling([50, 100], [0, 1], 50);

           $y = uniform_01scaling([50, 100], 50);

       They may also be called with a list or array of numbers:

           @cm_measures = uniform_scaling([0, 10000], [0, 25400], @in_measures);

           @melt_centigrade = uniform_scaling([0, 2000], [-273.15, 1726.85], \@melting_points);

       A number that is outside the original bounds will be proportionally changed to be outside
       of the new bounds, but then again having a number outside the original bounds is probably
       an error that should be checked before calling this function.

       <https://stats.stackexchange.com/q/281164>

       gcd

       hcf

       Return the greatest common divisor (also known as the highest common factor) of a list of
       integers. These are simply synomyms:

           $factor = gcd(@numbers);
           $factor = hcf(@numbers);

       lcm

       Return the least common multiple of a list of integers.

           $factor = lcm(@values);

       moduli()

       Return the moduli of an integer after repeated divisions. The remainders are returned in a
       list from left to right.

           @digits = moduli(1899, 10);   # Returns (9, 9, 8, 1)
           @rems = moduli(29, 3);        # Returns (2, 0, 0, 1)

   compare tag
       Create comparison functions for floating point (non-integer) numbers.

       Since exact comparisons of floating point numbers tend to be iffy, the comparison
       functions use a tolerance chosen by you. You may then use those functions from then on
       confident that comparisons will be consistent.

       If you do not provide a tolerance, a default tolerance of 1.49012e-8 (approximately the
       square root of an Intel Pentium's machine epsilon
       <https://en.wikipedia.org/wiki/Machine_epsilon>) will be used.

       generate_fltcmp()

       Returns a comparison function that will compare values using a tolerance that you supply.
       The generated function will return -1 if the first argument compares as less than the
       second, 0 if the two arguments compare as equal, and 1 if the first argument compares as
       greater than the second.

           my $fltcmp = generate_fltcmp(1.5e-7);

           my(@xpos) = grep {&$fltcmp($_, 0) == 1} @xvals;

       generate_relational()

       Returns a list of comparison functions that will compare values using a tolerance that you
       supply. The generated functions will be the equivalent of the equal, not equal, greater
       than, greater than or equal, less than, and less than or equal operators.

           my($eq, $ne, $gt, $ge, $lt, $le) = generate_relational(1.5e-7);

           my(@approx_5) = grep {&$eq($_, 5)} @xvals;

       Of course, if you were only interested in not equal, you could use:

           my(undef, $ne) = generate_relational(1.5e-7);

           my(@not_around5) = grep {&$ne($_, 5)} @xvals;

   polynomial tag
       Perform some polynomial operations on plain lists of coefficients.

           #
           # The coefficient lists are presumed to go from low order to high:
           #
           @coefficients = (1, 2, 4, 8);    # 1 + 2x + 4x**2 + 8x**3

       In all functions the coeffcient list is passed by reference to the function, and the
       functions that return coefficients all return references to a coefficient list.

       It is assumed that any leading zeros in the coefficient lists have already been removed
       before calling these functions, and that any leading zeros found in the returned lists
       will be handled by the caller. This caveat is particularly important to note in the case
       of "pl_div()".

       Although these functions are convenient for simple polynomial operations, for more
       advanced polynonial operations Math::Polynomial is recommended.

       pl_evaluate()

       Returns either a y-value for a corresponding x-value, or a list of y-values on the
       polynomial for a corresponding list of x-values, using Horner's method.

           $y = pl_evaluate(\@coefficients, $x);
           @yvalues = pl_evaluate(\@coefficients, @xvalues);

           @ctemperatures = pl_evaluate([-160/9, 5/9], @ftemperatures);

       The list of X values may also include X array references:

           @yvalues = pl_evaluate(\@coefficients, @xvalues, \@primes, $x, [-1, -10, -100]);

       pl_dxevaluate()

           ($y, $dy, $ddy) = pl_dxevaluate(\@coefficients, $x);

       Returns p(x), p'(x), and p"(x) of the polynomial for an x-value, using Horner's method.
       Note that unlike "pl_evaluate()" above, the function can only use one x-value.

       If the polynomial is a linear equation, the second derivative value will be zero.
       Similarly, if the polynomial is a simple constant, the first derivative value will be
       zero.

       pl_translate()

           $x = [8, 3, 1];
           $y = [3, 1];

           #
           # Translating C<x**2 + 3*x + 8> by C<x + 3> returns [26, 9, 1]
           #
           $z = pl_translate($x, $y);

       Returns a polynomial transformed by substituting a polynomial variable with another
       polynomial.  For example, a simple linear translation by 1 to the polynomial "x**3 + x**2
       + 4*x + 4" would be accomplished by setting x = (y - 1); resulting in "x**3 - 2*x**2 +
       5*x".

           $x = [4, 4, 1, 1];
           $y = [-1, 1];
           $z = pl_translate($x, $y);         # Becomes [0, 5, -2, 1]

       pl_add()

           $polyn_ref = pl_add(\@m, \@n);

       Add two lists of numbers as though they were polynomial coefficients.

       pl_sub()

           $polyn_ref = pl_sub(\@m, \@n);

       Subtract the second list of numbers from the first as though they were polynomial
       coefficients.

       pl_div()

           ($q_ref, $r_ref) = pl_div(\@numerator, \@divisor);

       Synthetic division for polynomials. Divides the first list of coefficients by the second
       list.

       Returns references to the quotient and the remainder.

       Remember to check for leading zeros (which are rightmost in the list) in the returned
       values. For example,

           my @n = (4, 12, 9, 3);
           my @d = (1, 3, 3, 1);

           my($q_ref, $r_ref) = pl_div(\@n, \@d);

       After division you will have returned "(3)" as the quotient, and "(1, 3, 0)" as the
       remainder. In general, you will want to remove the leading zero, or for that matter values
       within epsilon of zero, in the remainder.

           my($q_ref, $r_ref) = pl_div($f1, $f2);

           #
           # Remove any leading zeros (i.e., numbers smaller in
           # magnitude than machine epsilon) in the remainder.
           #
           my @remd = @{$r_ref};
           pop @remd while (@remd and abs($remd[$#remd]) < $epsilon);

           $f1 = $f2;
           $f2 = [@remd];

       If $f1 and $f2 were to go through that bit of code again, not removing the leading zeros
       would lead to a divide-by-zero error.

       If either list of coefficients is empty, pl_div() returns undefs for both quotient and
       remainder.

       pl_mult()

           $m_ref = pl_mult(\@coefficients1, \@coefficients2);

       Returns the reference to the product of the two multiplicands.

       pl_derivative()

           $poly_ref = pl_derivative(\@coefficients);

       Returns the derivative of a polynomial.

       pl_antiderivative()

           $poly_ref = pl_antiderivative(\@coefficients);

       Returns the antiderivative of a polynomial. The constant value is always set to zero and
       will need to be changed by the caller if a different constant is needed.

         my @coefficients = (1, 2, -3, 2);
         my $integral = pl_antiderivative(\@coefficients);

         #
         # Integral needs to be 0 at x = 1.
         #
         my @coeff1 = @{$integral};
         $coeff1[0] = - pl_evaluate($integral, 1);

AUTHOR

       John M. Gamble, "<jgamble at cpan.org>"

SEE ALSO

       Math::Polynomial for a complete set of polynomial operations, with the added convenience
       that objects bring.

       Among its other functions, List::Util has the mathematically useful functions max(),
       min(), product(), sum(), and sum0().

       List::MoreUtils has the function minmax().

       Math::Prime::Util has gcd() and lcm() functions, as well as vecsum(), vecprod(), vecmin(),
       and vecmax(), which are like the List::Util functions but which can force integer use, and
       when appropriate use Math::BigInt.

       Math::VecStat Likewise has min(), max(), sum() (which can take as arguments array
       references as well as arrays), plus maxabs(), minabs(), sumbyelement(), convolute(), and
       other functions.

BUGS

       Please report any bugs or feature requests to "bug-math-util at rt.cpan.org", or through
       the web interface at <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Math-Utils>.  I will
       be notified, and then you'll automatically be notified of progress on your bug as I make
       changes.

SUPPORT

       This module is on Github at <https://github.com/jgamble/Math-Utils>.

       You can also look for information at:

       •   RT: CPAN's request tracker (report bugs here)

           <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Math-Utils>

       •   MetaCPAN

           <https://metacpan.org/release/Math-Utils>

ACKNOWLEDGEMENTS

       To J. A. R. Williams who got the ball rolling with Math::Fortran.

LICENSE AND COPYRIGHT

       Copyright (c) 2017 John M. Gamble. All rights reserved. This program is free software; you
       can redistribute it and/or modify it under the same terms as Perl itself.