def calc_multifactor(returns, factors):
    """Computes multiple ordinary least squares linear fits, and returns
    fit parameters.

    Parameters
    ----------
    returns : pd.Series
        Daily returns of the strategy, noncumulative.
         - See full explanation in tears.create_full_tear_sheet.
    factors : pd.Series
        Secondary sets to fit.

    Returns
    -------
    pd.DataFrame
        Fit parameters.

    """
    import statsmodels.api as sm
    factors = factors.loc[returns.index]
    factors = sm.add_constant(factors)
    factors = factors.dropna(axis=0)
    results = sm.OLS(returns[factors.index], factors).fit()
    return results.params
