不能在 Algorithm::CurveFit 中使用对数项

Question

我正在尝试使用 Algorithm::CurveFit 来拟合一些数字。我有一个不寻常的安装，因为我在安装 Algorithm::CurveFit 时遇到问题：所以我的安装看起来与标准的必然不同。

代码如下：

sub curvefit {
    my ($args) = @_;
    my @undef_args = grep { !defined $args->{$_}} ('formula', 'parameters', 'x', 'y');
    if (scalar @undef_args > 0) {
        p @undef_args;
        die 'the above args are necessary, but were not defined.';
    }
    foreach my $key ('x', 'y') {
        if (scalar @{ $args->{$key} } == 0) {
            return 'no valid points'
        }
    }
    if ($args->{formula} !~ m/x/) {
        die "$args->{formula} must contain \"x\" in order to be interpreted."
    }
    $args->{max_iter} = $args->{max_iter} // 100; # maximum iterations
    my $square_residual = CurveFit->curve_fit( # "Algorithm::CurveFit" for users who could install the module
         formula            => $args->{formula}, # may be a Math::Symbolic tree instead
         params             => $args->{parameters},
         variable           => 'x',
         xdata              => $args->{x},
         ydata              => $args->{y},
         maximum_iterations => $args->{max_iter},
    );
    my %fit;
    $fit{function} = $args->{formula};
    foreach my $var (@{ $args->{parameters} }) {
        $fit{$var->[0]}{best}  = $var->[1];
        $fit{$var->[0]}{error} = $var->[2];
        $fit{function} =~ s/$var->[0]/$var->[1]/;
    }
    $fit{square_residual} = $square_residual;
    return \%fit
}

my @x = (1,2,3); # ensuring that 0 won't be fed to log to produce negative infinity
my @y = (10, 19, 33);

my $log_fit = curvefit({
    formula    => 'a * log(x) + b',
    parameters => [
    # name, guess, sufficient accuracy
        ['a', 0, 0.01],
        ['b', 1, 0.01],
    ],
    'x'        => \@x,
    'y'        => \@y
});

并在 Math::Symbolic 包中产生错误：

Can't call method "term_type" on an undefined value at /home/con/perl5/perlbrew/perls/perl-5.34.0/lib/site_perl/5.34.0/Math/Symbolic/Operator.pm line 595.
    Math::Symbolic::Operator::simplify(Math::Symbolic::Operator=HASH(0x564d6cebb830), 1) called at /home/con/perl5/perlbrew/perls/perl-5.34.0/lib/site_perl/5.34.0/Math/Symbolic/Operator.pm line 589
    Math::Symbolic::Operator::simplify(Math::Symbolic::Operator=HASH(0x564d6cebc470), 1) called at /home/con/perl5/perlbrew/perls/perl-5.34.0/lib/site_perl/5.34.0/Math/Symbolic/Operator.pm line 589
    Math::Symbolic::Operator::simplify(Math::Symbolic::Operator=HASH(0x564d6cebeed8), 1) called at /home/con/perl5/perlbrew/perls/perl-5.34.0/lib/site_perl/5.34.0/Math/Symbolic/Operator.pm line 589
    Math::Symbolic::Operator::simplify(Math::Symbolic::Operator=HASH(0x564d6bd209d8)) called at /home/con/perl5/perlbrew/perls/perl-5.34.0/lib/site_perl/5.34.0/x86_64-linux/CurveFit.pm line 123
    CurveFit::curve_fit("CurveFit", "formula", "a * log(x) + b", "params", ARRAY(0x564d6bcb2650), "variable", "x", "xdata", ...) called at 5.all.valid.pl line 33
    main::curvefit(HASH(0x564d6bcb26c8)) called at 5.all.valid.pl line 48
Command exited with non-zero status 255

转到 Math::Symbolic 中的那一行：

    my $tt2  = $o2->term_type();

我看不出这对调试问题有何帮助。

此外，Math::Symbolic似乎暗示我可以使用log条款：https://metacpan.org/pod/Math::Symbolic

如何在 CurveFit 子程序中使用对数？

Answer 1

来自 Math::Symbolic::Operator,

Supported operator symbols: (number of operands and their function in parens)
...
log => logarithm (2: base, function)
...

因此，自然对数的正确用法是 log(2.7182818284590452, x)

不能在 Algorithm::CurveFit 中使用对数项

Cannot use log terms in Algorithm::CurveFit

perl