A regression model with diagonal but non-identity covariance structure.
The weights are presumed to be (proportional to) the inverse of the variance of the observations. That is, if the variables are to be transformed by 1/sqrt(W) you must supply weights = 1/W. Note that this is different than the behavior for GLS with a diagonal Sigma, where you would just supply W.
Methods
Parameters : | endog : array-like
exog : array-like
weights : array-like, optional
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Notes
If the weights are a function of the data, then the postestimation statistics such as fvalue and mse_model might not be correct, as the package does not yet support no-constant regression.
Examples
>>> import numpy as np
>>> import scikits.statsmodels.api as sm
>>> Y = [1,3,4,5,2,3,4]
>>> X = range(1,8)
>>> X = sm.add_constant(X)
>>> wls_model = sm.WLS(Y,X, weights=range(1,8))
>>> results = wls_model.fit()
>>> results.params
array([ 0.0952381 , 2.91666667])
>>> results.tvalues
array([ 0.35684428, 2.0652652 ])
<T test: effect=2.9166666666666674, sd=1.4122480109543243, t=2.0652651970780505, p=0.046901390323708769, df_denom=5>
>>> print results.f_test([1,0])
<F test: F=0.12733784321528099, p=0.735774089183, df_denom=5, df_num=1>
Attributes
weights | array | The stored weights supplied as an argument. |
See regression.GLS |
Methods
fit(**kwargs[, method]) | Full fit of the model. |
hessian(params) | The Hessian matrix of the model |
information(params) | Fisher information matrix of model |
initialize() | |
loglike(params) | Returns the value of the gaussian loglikelihood function at params. |
predict(exog[, params]) | Return linear predicted values from a design matrix. |
score(params) | Score vector of model. |
whiten(X) | Whitener for WLS model, multiplies each column by sqrt(self.weights) |