It counts lines and maintains a sum of the values seen to date. When the key changes, it prints the average, then resets the line count and the sum. 
1    196       -> count = 1   sum = 196
1    190       -> count = 2   sum = 196+190
1    200       -> count = 3   sum = 196+190+200

 key changed, so print average, and reset count and sum

2    20        -> count = 1   sum = 20

 key changed, so print average, and reset count and sum

3    25        -> count = 1   sum = 25
3    19        -> count = 2   sum = 25+19
3    39        -> count = 3   sum = 25+19+39

 key changed, so print average, and reset count and sum

4    40        -> count = 1   sum = 40
4    41        -> count = 2   sum = 40+41
4    45        -> count = 3   sum = 40+41+45

 eof, so print average

[download]

In reply to Re^3: Data munging by ikegami
in thread Data munging by umasuresh

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.