使用perl查找中位数、众数、标准差？

Question

我有一个数字数组。计算数据集的中位数、众数和标准差的最简单方法是什么？

Answer 1

• Statistics::Basic::Mean
• Statistics::Basic::Median
• Statistics::Basic::Mode
• Statistics::Basic::StdDev

Answer 2

#!/usr/bin/perl
#
# stdev - figure N, min, max, median, mode, mean, & std deviation
#
# pull out all the real numbers in the input
# stream and run standard calculations on them.
# they may be intermixed with other test, need
# not be on the same or different lines, and 
# can be in scientific notion (avagadro=6.02e23).
# they also admit a leading + or -.
#
# Tom Christiansen
# tchrist@perl.com

use strict;
use warnings;

use List::Util qw< min max >;

sub by_number {
    if ($a < $b){ -1 } elsif ($a > $b) { 1 } else { 0 }
}


#
my $number_rx = qr{

  # leading sign, positive or negative
    (?: [+-] ? )

  # mantissa
    (?= [0123456789.] )
    (?: 
        # "N" or "N." or "N.N"
        (?:
            (?: [0123456789] +     )
            (?:
                (?: [.] )
                (?: [0123456789] * )
            ) ?
      |
        # ".N", no leading digits
            (?:
                (?: [.] )
                (?: [0123456789] + )
            ) 
        )
    )

  # abscissa
    (?:
        (?: [Ee] )
        (?:
            (?: [+-] ? )
            (?: [0123456789] + )
        )
        |
    )
}x;

my $n = 0;
my $sum = 0;
my @values = ();

my %seen = ();

while (<>) {
    while (/($number_rx)/g) {
        $n++;
        my $num = 0 + $1;  # 0+ is so numbers in alternate form count as same
        $sum += $num;
        push @values, $num;
        $seen{$num}++;
    } 
} 

die "no values" if $n == 0;

my $mean = $sum / $n;

my $sqsum = 0;
for (@values) {
    $sqsum += ( $_ ** 2 );
} 
$sqsum /= $n;
$sqsum -= ( $mean ** 2 );
my $stdev = sqrt($sqsum);

my $max_seen_count = max values %seen;
my @modes = grep { $seen{$_} == $max_seen_count } keys %seen;

my $mode = @modes == 1 
            ? $modes[0] 
            : "(" . join(", ", @modes) . ")";
$mode .= ' @ ' . $max_seen_count;

my $median;
my $mid = int @values/2;
my @sorted_values = sort by_number @values;
if (@values % 2) {
    $median = $sorted_values[ $mid ];
} else {
    $median = ($sorted_values[$mid-1] + $sorted_values[$mid])/2;
} 

my $min = min @values;
my $max = max @values;

printf "n is %d, min is %g, max is %g\n", $n, $min, $max;
printf "mode is %s, median is %g, mean is %g, stdev is %g\n", 
    $mode, $median, $mean, $stdev;

Answer 3

根据您需要走多远，erickb 的答案可能会奏效。但是对于 Perl 中的数字功能，有 PDL。您将使用 pdl 函数创建一个 piddle（包含您的数据的对象）。从那里您可以使用this page 上的操作来进行您需要的统计。

编辑：环顾四周，我发现两个函数调用完全符合您的需要。 statsover 提供 piddle 的一维统计信息，而 stats 对整个 piddle 进行相同的统计。

my $piddle = pdl @data;
my ($mean,$prms,$median,$min,$max,$adev,$rms) = statsover $piddle;