Cumulative standard deviation: Difference between revisions
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(→{{header|Perl}}: shorter version with closure) |
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} |
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print "std dev = $sd\n";</lang> |
print "std dev = $sd\n";</lang> |
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A much shorter version using a closure and a property of the variance: |
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<lang perl># <(x - <x>)²> = <x²> - <x>² |
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sub stddev; |
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{ |
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my @sum; |
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sub stddev { |
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my $x = shift; |
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$sum[0]++; |
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return sqrt( |
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($sum[2] += $x**2) / $sum[0] - |
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(($sum[1] += $x) / $sum[0])**2 |
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); |
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} |
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} |
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use feature qw(say); |
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say stddev $_ for 2, 4, 4, 4, 5, 5, 7, 9;</lang> |
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{{out}} |
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<pre>0 |
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1 |
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0.942809041582063 |
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0.866025403784439 |
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0.979795897113272 |
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1 |
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1.39970842444753 |
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2</pre> |
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=={{header|Perl 6}}== |
=={{header|Perl 6}}== |
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