I'm trying to figure out some warnings in the statsmodels test suite Why do the following raise RuntimeWarnings? np.linalg.det(np.ones((3,3))) C:\...\python-3.4.4.amd64\lib\site-packages\numpy\linalg\linalg.py:1776: RuntimeWarning: invalid value encountered in det r = _umath_linalg.det(a, signature=signature) Out[21]: 0.0 np.linalg.det(np.zeros((3,3))) C:\...\python-3.4.4.amd64\lib\site-packages\numpy\linalg\linalg.py:1776: RuntimeWarning: invalid value encountered in det r = _umath_linalg.det(a, signature=signature) Out[22]: 0.0 np.__version__ Out[23]: '1.11.2' and is there a way to distinguish those from user problems a = np.ones((3,3)) a[1,1] = np.nan np.linalg.det(a) C:\...\WinPython-64bit-3.4.4.5Qt5\python-3.4.4.amd64\lib\site-packages\numpy\linalg\linalg.py:1776: RuntimeWarning: invalid value encountered in det r = _umath_linalg.det(a, signature=signature) Out[26]: nan Josef