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# scikits.statsmodels.model.LikelihoodModelResults.cov_params

`LikelihoodModelResults.``cov_params`(r_matrix=None, column=None, scale=None, other=None)

  Returns the variance/covariance matrix.

  The variance/covariance matrix can be of a linear contrast of the estimates of params or all params multiplied by scale which will usually be an estimate of sigma^2. Scale is assumed to be a scalar.

  Parameters: | r_matrix : array-like Can be 1d, or 2d. Can be used alone or with other. column : array-like, optional Must be used on its own. Can be 0d or 1d see below. scale : float, optional Can be specified or not. Default is None, which means that the scale argument is taken from the model. other : array-like, optional Can be used when r_matrix is specified.
  Returns: | (The below are assumed to be in matrix notation.) : cov : ndarray If no argument is specified returns the covariance matrix of a model : (scale)*(X.T X)^(-1) : If contrast is specified it pre and post-multiplies as follows : (scale) * r_matrix (X.T X)^(-1) r_matrix.T : If contrast and other are specified returns : (scale) * r_matrix (X.T X)^(-1) other.T : If column is specified returns : (scale) * (X.T X)^(-1)[column,column] if column is 0d : OR : (scale) * (X.T X)^(-1)[column][:,column] if column is 1d :

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