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62 lines
1.5 KiB
62 lines
1.5 KiB
import { determination } from "./utils/determination";
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import { interpose } from "./utils/interpose";
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import { ols } from "./utils/ols";
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import { visitPoints } from "./utils/points";
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export default function() {
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let x = d => d[0],
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y = d => d[1],
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domain;
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function exponential(data){
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let n = 0,
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Y = 0,
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YL = 0,
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XY = 0,
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XYL = 0,
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X2Y = 0,
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xmin = domain ? +domain[0] : Infinity,
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xmax = domain ? +domain[1] : -Infinity;
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visitPoints(data, x, y, (dx, dy) => {
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const ly = Math.log(dy), xy = dx * dy;
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++n;
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Y += (dy - Y) / n;
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XY += (xy - XY) / n;
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X2Y += (dx * xy - X2Y) / n;
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YL += (dy * ly - YL) / n;
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XYL += (xy * ly - XYL) / n;
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if (!domain){
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if (dx < xmin) xmin = dx;
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if (dx > xmax) xmax = dx;
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}
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});
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let [a, b] = ols(XY / Y, YL / Y, XYL / Y, X2Y / Y);
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a = Math.exp(a);
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const fn = x => a * Math.exp(b * x),
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out = interpose(xmin, xmax, fn);
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out.a = a;
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out.b = b;
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out.predict = fn;
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out.rSquared = determination(data, x, y, Y, fn);
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return out;
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}
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exponential.domain = function(arr){
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return arguments.length ? (domain = arr, exponential) : domain;
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}
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exponential.x = function(fn){
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return arguments.length ? (x = fn, exponential) : x;
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}
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exponential.y = function(fn){
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return arguments.length ? (y = fn, exponential) : y;
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}
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return exponential;
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}
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