statsmodels.tools.tools.add_constant¶
-
statsmodels.tools.tools.
add_constant
(data, prepend=True, has_constant='skip')[source]¶ Add a column of ones to an array.
- Parameters
data : array_like
A column-ordered design matrix.
prepend : bool
If true, the constant is in the first column. Else the constant is appended (last 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 constant 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. Returned value type depends on input type.
Notes
When the input is recarray or a pandas Series or DataFrame, the added column’s name is ‘const’.