Basically, you're trying to find the regresssion for the function: 
sales = base_sale + K * log( i )
where K = multiple/log( logbase ). There's no way by regression alone to determine multiple or logbase separately.

The above regression is not strictly linear, but if you tranform i to x via 

 x = log i
(or 
i = e^x
), then you get: 
sales = base_sale + K * x
which is a straight linear regression once you apply the transform correctly to your interval variable. Thus, you simply have to do some stat summation over your data set, and you're all set; the exact equations for that should be in any numerical math text (I don't see any Perl modules that do regression easily, but the routine isn't hard for this).

-----------------------------------------------------
Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
"I can see my house from here!"
It's not what you know, but knowing how to find it if you don't know that's important

In reply to Re: Numerical Analysis Challenge by Masem
in thread Numerical Analysis Challenge by tomazos

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.