DataFrame.diff on datetime64 returns result inconsistent with Series.diff (original) (raw)

Code Sample, a copy-pastable example if possible

pd.Series(['NaT', '2019-01-01', '2019-01-02'], dtype='datetime64[ns]').diff() 0 NaT 1 NaT 2 1 days dtype: timedelta64[ns]

pd.Series(['NaT', '2019-01-01', '2019-01-02'], dtype='datetime64[ns]').to_frame().diff() 0 0 NaT 1 -88855 days +00:12:43.145224 2 1 days 00:00:00

Problem description

Doing .diff() on a DataFrame of datetime64 should yield exactly time deltas in exactly the same way as on the Series i.e. index (1,0) in the DataFrame above should be NaT, not an overflown timedelta64.

Output of pd.show_versions()

DetailsINSTALLED VERSIONS ------------------ commit : None python : 3.8.1.final.0 python-bits : 64 OS : Windows OS-release : 10 machine : AMD64 processor : Intel64 Family 6 Model 63 Stepping 2, GenuineIntel byteorder : little LC_ALL : None LANG : None LOCALE : English_United Kingdom.936

pandas : 1.0.1
numpy : 1.18.1
pytz : 2019.3
dateutil : 2.8.1
pip : 20.0.2
setuptools : 45.2.0.post20200210
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : None
IPython : None
pandas_datareader: None
bs4 : None
bottleneck : None
fastparquet : None
gcsfs : None
lxml.etree : None
matplotlib : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pytables : None
pytest : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
xlsxwriter : None
numba : None