It seems that when comparing two Series objects, index is ignored, here is an trivial example
In [177]: pd.show_versions()
INSTALLED VERSIONS
------------------
commit: None
python: 2.7.7.final.0
python-bits: 64
OS: Linux
OS-release: 3.2.0-0.bpo.4-amd64
machine: x86_64
processor:
byteorder: little
LC_ALL: None
LANG: en_US
pandas: 0.14.0
nose: 1.3.0
Cython: 0.19.2
numpy: 1.8.1
scipy: 0.14.0
statsmodels: 0.5.0
IPython: 2.0.0
sphinx: 1.1.3
patsy: 0.2.1
scikits.timeseries: None
dateutil: 1.5
pytz: 2014.3
bottleneck: None
tables: 3.0.0
numexpr: 2.2.2
matplotlib: 1.3.1
openpyxl: 1.6.2
xlrd: 0.9.2
xlwt: 0.7.5
xlsxwriter: None
lxml: 3.2.3
bs4: 4.3.1
html5lib: None
bq: None
apiclient: None
rpy2: None
sqlalchemy: 0.8.3
pymysql: None
psycopg2: None
In [158]: a = pd.Series([100, 101, 102, 103], index=[1,2,3,4])
In [168]: b = pd.Series([102, 103, 104, 105], index=[3, 4, 5, 6])
In [170]: a
Out[170]:
1 100
2 101
3 102
4 103
dtype: int64
In [171]: b
Out[171]:
3 102
4 103
5 104
6 105
dtype: int64
In [172]: a > b
Out[172]:
1 False
2 False
3 False
4 False
dtype: bool
In [173]: a < b
Out[173]:
1 True
2 True
3 True
4 True
dtype: bool
In [174]: a == b
Out[174]:
1 False
2 False
3 False
4 False
dtype: bool
In [175]: a - b
Out[175]:
1 NaN
2 NaN
3 0
4 0
5 NaN
6 NaN
dtype: float64
Comment From: jreback
see discussion here: https://github.com/pydata/pandas/issues/1134
This is a feature!
Comment From: longislandfarmer
Thanks for the link, can this be documented/highlighted in documentation? It's really not obvious!
Comment From: jorisvandenbossche
@jreback you say it is a feature, but we discussed it in the issue you referenced, and you also had a PR https://github.com/pydata/pandas/pull/6860 that had the intention to change this?
Comment From: jreback
@jorisvandenbossche I know, but I don't think its easy to change this, so can't happen in 0.15.0 maybe later. let's just document for now.
@mjnicky want to take a stab at this?
Comment From: jorisvandenbossche
This was fixed in https://github.com/pandas-dev/pandas/pull/13894 for 0.19.0