// Wikipedia: https://en.wikipedia.org/wiki/Mean_squared_error
const meanSquaredError = (predicted, expected) => {
if (!Array.isArray(predicted) || !Array.isArray(expected)) {
throw new TypeError('Argument must be an Array')
}
if (predicted.length !== expected.length) {
throw new TypeError('The two lists must be of equal length')
}
let err = 0
for (let i = 0; i < expected.length; i++) {
err += (expected[i] - predicted[i]) ** 2
}
return err / expected.length
}
export { meanSquaredError }