// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Incoprea
// Fit a trend line through paired values
// Not compiled or tested in-world
// Setup: Put in a spare prim you own. Edit alternating x/y numbers in DATA and touch.
// Stop / restore: Disable or remove the script. It only reports to its owner and does not change prim properties. Reset clears its temporary state.
// Notes: A least-squares fit is descriptive, not predictive assurance. At least two pairs with varying x are needed; small samples can be unstable.
// License: see LICENSE in this distribution.
// Original Incoprea example. MIT. Owner-only calculation; no scene changes.
list DATA=[0.0,1.2,1.0,2.9,2.0,5.1,3.0,6.8];
default
{
    touch_start(integer detectedCount)
    {
        if (llDetectedKey(0) != llGetOwner()) return;
        integer length=llGetListLength(DATA);
        if (length<4 || length%2)
        {
            llOwnerSay("Need at least two x/y pairs.");
            return;
        }
        float n=(float)(length/2);
        float sx;
        float sy;
        float sxx;
        float sxy;
        integer i;
        for (i=0; i<length; i+=2)
        {
            float x=llList2Float(DATA,i);
            float y=llList2Float(DATA,i+1);
            sx+=x;
            sy+=y;
            sxx+=x*x;
            sxy+=x*y;
        }
        float denominator=n*sxx-sx*sx;
        if (llFabs(denominator)<0.000001)
        {
            llOwnerSay("X values do not vary enough.");
            return;
        }
        float slope=(n*sxy-sx*sy)/denominator;
        llOwnerSay("Slope="+(string)slope+"; intercept="+(string)((sy-slope*sx)/n));
    }
    changed(integer change)
    {
        if (change & CHANGED_OWNER) llResetScript();
    }
}