statsmodels.robust.norms.AndrewWave.psi¶

AndrewWave.psi(z)[source]¶

The psi function for Andrew’s wave

The analytic derivative of rho

Parameters:¶

z : array_like¶

1d array

Returns:¶

psi – psi(z) = a * sin(z/a) for |z| <= a*pi

psi(z) = 0 for |z| > a*pi

Return type:¶

ndarray