From: William James <w_a_x_man@...>
Date: 2006-12-02T19:45:08+09:00
Subject: Re: calculations on lists of numbers

ara.t.howard@noaa.gov wrote:
> for years i've felt that i should be able to pipe numerical output into some
> unix command like so
>
>    cat list | mean
>    cat list | sum
>    cat list | minmax

Why drag in the cat when it's utterly superfluous?

  mean <list
  sum <list
  minmax <list

>
> etc.
>
> and have never found one.  right now i'm building a ruby version - before i
> continue, does anyone know a standard unix or ruby version of this?


Matthew Moss wrote:
> >    cat list | mean
>
> cat list | awk '{ s += $1; n += 1 } END { print s / n }'

Reading a file isn't a magical ability; awk can do it.

  awk "{s+=$0} END{print s/NR}" list

If there can be more than one number on a line:

  awk "{for(i=1;i<=NF;i++)s+=$i; n+=NF} END{print s/n}" file

Ruby:

ruby -nale "BEGIN{$s=$n=0}; $s+=$F.inject(0){|x,y| x.to_f+y.to_f};
  $n+=$F.size; END{puts $s/$n}" file

If there's memory enough for the whole file:

ruby -e "a=$<.read.split.map{|x|x.to_f};
  puts a.inject{|x,y|x+y}/a.size" file