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Thread: Item value interpolation formula

  1. #1

    Item value interpolation formula

    It can easily be proven that value of item isn't linearly interpolated. Anyone know what type of interpolation is used for this?
    Ekarona 220/30 Female Solitus Engineer, long term member of Northern Star and proper "poor" gimp.
    Ekaslave 220/low Female Solitus Trader, FLAT(TM) pricing TS, almost all can do!
    Ekaros almost there/almost there too Male Solitus Martial-Artist.
    Ekadv gimp/gimp Female Opifex Adventurer

  2. #2
    I thought item values are linearly interpolated, but between break points, which are not distributed across an item's entire range of QLs linearly.

    Some item values only change across these break points (for instance, the int buff of OET pistols only change at these break points), and when dealing with the fractional parts, I believe the fractional part of the number is simply truncated rather than rounded.

    My calculations are sometimes off by one in one direction or another. I think it comes down to places where numbers are being truncated in the middle of the interpolation calculation. But what are you observing that makes you think the interpolation is completely non-linear?
    Froobalicious General of Barador Arin.

    -- Playing AO for six years, still a nuub gimp, and proud of it!

  3. #3
    https://docs.google.com/spreadsheets...ocVc4Q/pubhtml

    For Portable Surgery Clinic which only has high and low entries. (1QL entry calculated from item entry)

    The base price was calculated via: Shop_price/(shop modifier) *(1-CL_modifier)

    CL_modifier is 0.01 per 40CL.

    The chart shows non-linear correlation.
    Ekarona 220/30 Female Solitus Engineer, long term member of Northern Star and proper "poor" gimp.
    Ekaslave 220/low Female Solitus Trader, FLAT(TM) pricing TS, almost all can do!
    Ekaros almost there/almost there too Male Solitus Martial-Artist.
    Ekadv gimp/gimp Female Opifex Adventurer

  4. #4
    I guess nobody else wanted to chime in on this. I've never tried to interpolate on the shop price field, so your information is news to me.

    The problem with non-linear interpolation is that once the relationship is non-linear, then there are virtually endless possibilities that would fit the data. Without knowing the actual function, we could probably take a guess and fit the data. The plot you have looks like a second order polynomial. I'll look around to see if Google Sheets has a polynomial fit function.
    Froobalicious General of Barador Arin.

    -- Playing AO for six years, still a nuub gimp, and proud of it!

  5. #5
    Ok, easiest way to do it in Google Sheets is described in this YouTube video:

    https://www.youtube.com/watch?v=--1-cfnicJ8
    Froobalicious General of Barador Arin.

    -- Playing AO for six years, still a nuub gimp, and proud of it!

  6. #6
    I've been trying to figure out that formula for a while, but no luck. There is one posted here that's close: http://auno.org/forum.php?cmd=show&thread=1369, but more then half of the interpolated values are off by 1.

  7. #7
    Quote Originally Posted by Lucier View Post
    I've been trying to figure out that formula for a while, but no luck. There is one posted here that's close: http://auno.org/forum.php?cmd=show&thread=1369, but more then half of the interpolated values are off by 1.
    Thanks.

    I think there is some rounding due to how price modifiers work.

    Following link formula should be:
    Value = Vl+ (Q-Ql)^2 * (Vh-Vl) / (Qh - Ql)^2

    Where
    Vl is low QL value
    Vh is high QL value
    Ql low QL
    Qh High QL
    Q desired QL
    Last edited by Ekarona; Dec 13th, 2015 at 16:29:10.
    Ekarona 220/30 Female Solitus Engineer, long term member of Northern Star and proper "poor" gimp.
    Ekaslave 220/low Female Solitus Trader, FLAT(TM) pricing TS, almost all can do!
    Ekaros almost there/almost there too Male Solitus Martial-Artist.
    Ekadv gimp/gimp Female Opifex Adventurer

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