File size: 346 Bytes
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export default function(polygon) {
var i = -1,
n = polygon.length,
x = 0,
y = 0,
a,
b = polygon[n - 1],
c,
k = 0;
while (++i < n) {
a = b;
b = polygon[i];
k += c = a[0] * b[1] - b[0] * a[1];
x += (a[0] + b[0]) * c;
y += (a[1] + b[1]) * c;
}
return k *= 3, [x / k, y / k];
}
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