SUR Models

class SUR:
    def __init__(self, bigy, bigX, df_name=None, sur_constant=True, name_bigy=None, 
                 name_bigX=None, name_ds=None, vm=False, latex=False):
        """
        Seemingly unrelated regressions.
        
        Parameters:
        - bigy (array): Stacked dependent variables for all equations
        - bigX (array): Stacked independent variables for all equations
        - df_name (list): Names for each equation
        - sur_constant (bool): Include constant terms
        """

class SURerrorGM:
    def __init__(self, bigy, bigX, w, df_name=None, sur_constant=True):
        """SUR with spatial error structure using GMM estimation."""

class SURerrorML:
    def __init__(self, bigy, bigX, w, df_name=None, sur_constant=True):
        """SUR with spatial error structure using ML estimation."""

class SURlagIV:
    def __init__(self, bigy, bigX, w, df_name=None, sur_constant=True):
        """SUR with spatial lag structure using IV estimation."""