@bokeh/bokehjs
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Interactive, novel data visualization
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JavaScript
import { infer_type } from "../types";
import { assert } from "./assert";
export function catmullrom_spline(x, y, T = 10, tension = 0.5, closed = false) {
/** Centripetal Catmull-Rom spline. */
assert(x.length == y.length);
const n = x.length;
const N = closed ? n + 1 : n;
const ArrayType = infer_type(x, y);
const xx = new ArrayType(N + 2);
const yy = new ArrayType(N + 2);
xx.set(x, 1);
yy.set(y, 1);
if (closed) {
xx[0] = x[n - 1];
yy[0] = y[n - 1];
xx[N] = x[0];
yy[N] = y[0];
xx[N + 1] = x[1];
yy[N + 1] = y[1];
}
else {
xx[0] = x[0];
yy[0] = y[0];
xx[N + 1] = x[n - 1];
yy[N + 1] = y[n - 1];
}
const basis = new ArrayType(4 * (T + 1));
for (let j = 0, k = 0; j <= T; j++) {
const t = j / T;
const t_2 = t ** 2;
const t_3 = t * t_2;
basis[k++] = 2 * t_3 - 3 * t_2 + 1; // h00
basis[k++] = -2 * t_3 + 3 * t_2; // h01
basis[k++] = t_3 - 2 * t_2 + t; // h10
basis[k++] = t_3 - t_2; // h11
}
const xt = new ArrayType((N - 1) * (T + 1));
const yt = new ArrayType((N - 1) * (T + 1));
for (let i = 1, k = 0; i < N; i++) {
const t0x = (xx[i + 1] - xx[i - 1]) * tension;
const t0y = (yy[i + 1] - yy[i - 1]) * tension;
const t1x = (xx[i + 2] - xx[i]) * tension;
const t1y = (yy[i + 2] - yy[i]) * tension;
for (let j = 0; j <= 4 * T; k++) {
const h00 = basis[j++];
const h01 = basis[j++];
const h10 = basis[j++];
const h11 = basis[j++];
xt[k] = h00 * xx[i] + h01 * xx[i + 1] + h10 * t0x + h11 * t1x;
yt[k] = h00 * yy[i] + h01 * yy[i + 1] + h10 * t0y + h11 * t1y;
}
}
return [xt, yt];
}
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