Brianegge: Created page with 'This handy script calcs the standard deviation of a list of numbers from the standard input. Example: ping google.com | ruby -ne 'if $_ =~ /time(\d+)ms/ the…'

2009-10-20T07:22:03Z

Created page with 'This handy script calcs the standard deviation of a list of numbers from the standard input. Example: <geshi lang="bash"> ping google.com | ruby -ne 'if $_ =~ /time(\d+)ms/ the…'

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This handy script calcs the standard deviation of a list of numbers from the standard input. Example:

<geshi lang="bash">
ping google.com | ruby -ne 'if $_ =~ /time(\d+)ms/ then puts $1 end' | stddev
count mean stddev
4 48.33 34.39
</geshi>

<geshi lang="ruby">
#!/bin/env ruby

def variance(population)
n = 0
mean = 0.0
s = 0.0
population.each { |x|
n = n + 1
delta = x - mean
mean = mean + (delta / n)
s = s + delta * (x - mean)
}
# if you want to calculate std deviation
# of a sample change this to "s / (n-1)"
return s / n
end

def mean(population)
n = 0
mean = 0.0
population.each { |x|
n = n + 1
delta = x - mean
mean = mean + (delta / n)
}
return mean
end
# calculate the standard deviation of a population
# accepts: an array, the population
# returns: the standard deviation
def standard_deviation(population)
Math.sqrt(variance(population))
end

values = []
$<.each do |l|
values << l.to_f
end

puts ["count", "mean", "stddev"].join("\t")
puts "%d\t%.2f\t%.2f" % [values.size(), mean(values), standard_deviation(values)]
</geshi>

[[Category:Ruby]]

Stddev - Revision history

Brianegge: Created page with 'This handy script calcs the standard deviation of a list of numbers from the standard input. Example: ping google.com | ruby -ne 'if $_ =~ /time(\d+)ms/ the…'