import pl from "npm:nodejs-polars";

export function residuals(x: pl.Expr, y: pl.Expr): pl.Expr {
  const xM = x.minus(x.mean());
  const yM = y.minus(y.mean());
  const xMSQ = xM.pow(2);
  const beta = xM.dot(yM).div(xMSQ.sum());
  return yM.minus(beta.mul(xM));
}