Tengo un DataFrame de pandas como este: a b 2011-01-01 00:00:00 1.883381 -0.416629 2011-01-01 01:00:00 0.149948 -1.782170 2011-01-01 02:00:00 -0.407604 0.314168 2011-01-01 03:00:00 1.452354 NaN 2011-01-01 04:00:00 -1.224869 -0.947457 2011-01-01 05:00:00 0.498326 0.070416 2011-01-01 06:00:00...