理解statsmodels.tools.tools.add_constant

• statsmodels.tools.tools.add_constant(data, prepend=True, has_constant=‘skip’)

  Add a column of ones to an array.

  Parameter	type	mean
  data	array_like	A column-ordered design matrix
  prepend	bool	If True, the constant is in the first column
  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 any column has a constnat value. Using ‘add’ will add a column of 1s if a constant column is present.

  Returns : array_like

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