Hi, as previously discussed on the mailing list http://numpy-discussion.10968.n7.nabble.com/Inconsistent-results-for-the-cov... and listed in the issude https://github.com/numpy/numpy/issues/11196 there is no-standard factor to the scaling of the covariance matrix in np.polyfit. A while ago, I posted the pull request https://github.com/numpy/numpy/pull/11197 that removes the non-standard factor and introduces an option to give out the unscaled covariance. After an inital review by Marten van Kerkwijk, the only problem left was the question about the api. I have not heard back in while and was wondering whether there is still interest in this PR. Greetings Andreas