method
TrimmedMean.
rho
The robust criterion function for least trimmed mean.
1d array
rho(z) = (1/2.)*z**2 for |z| <= c
rho(z) = 0 for |z| > c
statsmodels.robust.norms.TrimmedMean.psi_deriv
statsmodels.robust.norms.TrimmedMean.weights