On your first change, you appear to be using $diff with the same meaning. But, subtracting out $original later doesn't do the same thing as calculating the running $delta. I suppose it's a quirk that the example gave the same results!!

If the total is a+b+c+d, then the given data is (total, b-a, c-b, d-c). This means that the missing "original" a is total- (a+(b-a) + (a+(b-a))+(c-b) + ((a+(b-a))+(c-b))+(d-c))) divided by the number of elements.

Hmm, cancelling out, I see (b + c + d), but you are computing ( (b-a) + (c-b) + (d-c) ), the sum of the listed deltas. That gives you (d-a) which is the unknown first value (a) subtracted from the last value, which we don't know either.

It is a total coincedecne that the sum of the deltas happens to be the same as the difference between the first and last result elements.

In reply to Results? by John M. Dlugosz
in thread Perl Drag Racing - sum/delta list by John M. Dlugosz

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.