tools.tools.add_constant()

statsmodels.tools.tools.add_constant

statsmodels.tools.tools.add_constant(data, prepend=True, has_constant='skip') [source]

This appends a column of ones to an array if prepend==False.

Parameters:

data : array-like data is the column-ordered design matrix prepend : bool True and the constant is prepended rather than appended. has_constant : str {?raise?, ?add?, ?skip?} Behavior if ``data?? already has a constant. The default will return data without adding another constant. If ?raise?, will raise an error if a constant is present. Using ?add? will duplicate the constant, if one is present. Has no effect for structured or recarrays. There is no checking for a constant in this case.

Returns:

data : array The original array with a constant (column of ones) as the first or last column.