statsmodels.robust.norms.LeastSquares.psi#
- LeastSquares.psi(z)[source]#
The psi function for the least squares estimator
The analytic derivative of rho.
\[\psi(z) = z\]- Parameters:
- zarray_like
1d array
- Returns:
- psi
ndarray The value of the psi function.
- psi