G'day hdb,

... the documentation of Algorithm::CurveFit seems to specify that powers need to be written as x^n and not x**n.

Firstly, I will say that the first line of code in the Algorithm::CurveFit SYNOPSIS: 

my $formula = 'c + a * x^2';

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is written in a way that suggests this intent 

$ perl -MO=Deparse,-p -e 'my $formula = $c + $a * $x**2;'
(my $formula = ($c + ($a * ($x ** 2))));
-e syntax OK

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more than it does this one 

$ perl -MO=Deparse,-p -e 'my $formula = $c + $a * $x^2;'
(my $formula = (($c + ($a * $x)) ^ 2));
-e syntax OK

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However, further down they have

The formula should be a string that can be parsed by Math::Symbolic.

The doco for that module has

Warning: The operator to use for exponentiation is the normal Perl operator for exponentiation **, NOT the caret ^ which denotes exponentiation in the notation that is recognized by the Math::Symbolic parsers! The ^ operator will be interpreted as the normal binary xor.

[Update (cosmetic): 2 instances of quoting my own code — <blockquote>s removed.]

-- Ken

In reply to Re^2: fitting double lognormal distribution on a dataset by kcott
in thread fitting double lognormal distribution on a dataset by sdani

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