Notebooks 2.0 is here.
News and graphics at @ClimateLab, a project of @PostGraphics.
vecmath = ({
abs,
add,
sub,
mult,
div,
limit,
normalize,
setMag,
getMag,
dot,
project,
ang,
dist,
trans,
invalid
});
abs = v => {
const out = [];
for (let i = 0; i < v.length; i++){
out[i] = Math.abs(v[i]);
}
return out;
}
// Add vector w to vector v
add = (v, w) => {
let out = [];
for (let i = 0; i < v.length; i++){
out[i] = v[i] + w[i];
}
return out;
}
// Subtract vector w from vector v
sub = (v, w) => {
let out = [];
for (let i = 0; i < v.length; i++){
out[i] = v[i] - w[i];
}
return out;
}
// Multiply vector v by w, either a vector of equal length or a scalar
mult = (v, w) => {
let that = [];
if (typeof w === "number"){
for (let i = 0; i < v.length; i++){
that[i] = w;
}
}
else {
that = w;
}
let out = [];
for (let i = 0; i < v.length; i++){
out[i] = v[i] * that[i];
}
return out;
}
// Divide vector v by w, either a vector of equal length or a scalar
div = (v, w) => {
let that = [];
if (typeof w === "number"){
for (let i = 0; i < v.length; i++){
that[i] = w;
}
}
else {
that = w;
}
let out = [];
for (let i = 0; i < v.length; i++){
out[i] = v[i] / that[i];
}
return out;
}
// Limit the magnitude of this vector to the value used for the n parameter.
limit = (v, n) => {
let out = v;
const sq = Math.pow(getMag(v), 2);
if (sq > n * n){
out = div(out, Math.sqrt(sq));
out = mult(out, n);
}
return out;
}
// Normalize the vector to length 1 (make it a unit vector).
normalize = v => {
const m = getMag(v), l = v.length;
return m ? mult(v, 1 / m) : v.map(d => 1 / l);
}
// Get the magnitude of a vector
getMag = v => {
let l = v.length, sums = 0;
for (let i = 0; i < l; i++){
sums += v[i] * v[i];
}
return Math.sqrt(sums);
}
// Set the magnitude of this vector to the value used for the n parameter.
setMag = (v, n) => {
return mult(normalize(v), n);
}
// Compute the dot product or inner product
dot = (v1, v2) => {
let o = 0;
for (let i = 0, l = v1.length; i < l; i++){
o += v1[i] * v2[i];
}
return o;
}
// Projects vector v1 onto vector v2
project = (v1, v2) => {
return mult(v2, dot(v1, v2) / dot(v2, v2))
}
// Angle from vector v to vector w in radians
// Only works for 2d vectors
ang = (v, w) => Math.atan2(w[1] - v[1], w[0] - v[0]);
dist([2, 1], project([2, 1], [6, 8]))
Math.pow(2 - 6/5, 2) + Math.pow(1 - 8/5, 2)
// Distance from position of vector v to position of vector w in pixels
dist = (v, w) => {
let sum = 0;
for (let i = 0, l = v.length; i < l; i++){
sum += Math.pow(w[i] - v[i], 2);
}
return Math.sqrt(sum);
}
// Translate position of vector v by an angle in radians and a distance in pixels
trans = (v, ang, dist) => [v[0] + dist * Math.cos(ang), v[1] + dist * Math.sin(ang)];
invalid = v => {
let out = false;
for (let i = 0, l = v.length; i < l; i++){
const d = v[i];
if (typeof d !== "number" || !isFinite(d)) {
out = true;
break;
}
}
return out;
}
sqrt = Math.sqrt
Purpose-built for displays of data
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