.. _whatsnew_0151:

v0.15.1 (November 9, 2014)
--------------------------

This is a minor bug-fix release from 0.15.0 and includes a small number of API changes, several new features,
enhancements, and performance improvements along with a large number of bug fixes. We recommend that all
users upgrade to this version.

- :ref:`Enhancements <whatsnew_0151.enhancements>`
- :ref:`API Changes <whatsnew_0151.api>`
- :ref:`Bug Fixes <whatsnew_0151.bug_fixes>`

.. _whatsnew_0151.api:

API changes
~~~~~~~~~~~

- Represent ``MultiIndex`` labels with a dtype that utilizes memory based on the level size. In prior versions, the memory usage was a constant 8 bytes per element in each level. In addition, in prior versions, the *reported* memory usage was incorrect as it didn't show the usage for the memory occupied by the underling data array. (:issue:`8456`)

  .. ipython:: python

     dfi = DataFrame(1,index=pd.MultiIndex.from_product([['a'],range(1000)]),columns=['A'])

  previous behavior:

  .. code-block:: python

     # this was underreported in prior versions
     In [1]: dfi.memory_usage(index=True)
     Out[1]:
     Index    8000 # took about 24008 bytes in < 0.15.1
     A        8000
     dtype: int64


  current behavior:

  .. ipython:: python

     dfi.memory_usage(index=True)

- ``groupby`` with ``as_index=False`` will not add erroneous extra columns to
  result (:issue:`8582`):

  .. ipython:: python

    np.random.seed(2718281)
    df = pd.DataFrame(np.random.randint(0, 100, (10, 2)),
                      columns=['jim', 'joe'])
    df.head()

    ts = pd.Series(5 * np.random.randint(0, 3, 10))

  previous behavior:

  .. code-block:: python

     In [4]: df.groupby(ts, as_index=False).max()
     Out[4]:
        NaN  jim  joe
     0    0   72   83
     1    5   77   84
     2   10   96   65

  current behavior:

  .. ipython:: python

    df.groupby(ts, as_index=False).max()

- ``groupby`` will not erroneously exclude columns if the column name conflics
  with the grouper name (:issue:`8112`):

  .. ipython:: python

     df = pd.DataFrame({'jim': range(5), 'joe': range(5, 10)})
     df
     gr = df.groupby(df['jim'] < 2)

  previous behavior (excludes 1st column from output):

  .. code-block:: python

     In [4]: gr.apply(sum)
     Out[4]:
            joe
     jim
     False   24
     True    11

  current behavior:

  .. ipython:: python

     gr.apply(sum)

- ``concat`` permits a wider variety of iterables of pandas objects to be
  passed as the first parameter (:issue:`8645`):

  .. ipython:: python

     from collections import deque
     df1 = pd.DataFrame([1, 2, 3])
     df2 = pd.DataFrame([4, 5, 6])

  previous behavior:

  .. code-block:: python

     In [7]: pd.concat(deque((df1, df2)))
     TypeError: first argument must be a list-like of pandas objects, you passed an object of type "deque"

  current behavior:

  .. ipython:: python

     pd.concat(deque((df1, df2)))

- ``s.dt.hour`` and other ``.dt`` accessors will now return ``np.nan`` for missing values (rather than previously -1), (:issue:`8689`)

  .. ipython:: python

     s = Series(date_range('20130101',periods=5,freq='D'))
     s.iloc[2] = np.nan
     s

  previous behavior:

  .. code-block:: python

     In [6]: s.dt.hour
     Out[6]:
     0    0
     1    0
     2   -1
     3    0
     4    0
     dtype: int64

  current behavior:

  .. ipython:: python

     s.dt.hour

- support for slicing with monotonic decreasing indexes, even if ``start`` or ``stop`` is
  not found in the index (:issue:`7860`):

  .. ipython:: python

    s = pd.Series(['a', 'b', 'c', 'd'], [4, 3, 2, 1])
    s

  previous behavior:

  .. code-block:: python

    In [8]: s.loc[3.5:1.5]
    KeyError: 3.5

  current behavior:

  .. ipython:: python

    s.loc[3.5:1.5]

- added Index properties `is_monotonic_increasing` and `is_monotonic_decreasing` (:issue:`8680`).


.. note:: io.data.Options has been fixed for a change in the format of the Yahoo Options page (:issue:`8612`), (:issue:`8741`)

  As a result of a change in Yahoo's option page layout, when an expiry date is given,
  ``Options`` methods now return data for a single expiry date.  Previously, methods returned all
  data for the selected month.

  The ``month`` and ``year`` parameters have been undeprecated and can be used to get all
  options data for a given month.

  If an expiry date that is not valid is given, data for the next expiry after the given
  date is returned.

  Option data frames are now saved on the instance as ``callsYYMMDD`` or ``putsYYMMDD``.  Previously
  they were saved as ``callsMMYY`` and ``putsMMYY``.  The next expiry is saved as ``calls`` and ``puts``.

  New features:

  The expiry parameter can now be a single date or a list-like object containing dates.

  A new property ``expiry_dates`` was added, which returns all available expiry dates.

  current behavior:

  .. ipython:: python

     from pandas.io.data import Options
     aapl = Options('aapl','yahoo')
     aapl.get_call_data().iloc[0:5,0:1]
     aapl.expiry_dates
     aapl.get_near_stock_price(expiry=aapl.expiry_dates[0:3]).iloc[0:5,0:1]

  See the Options documentation in :ref:`Remote Data  <remote_data.yahoo_options>`

.. _whatsnew_0151.datetime64_plotting:

- pandas now also registers the ``datetime64`` dtype in matplotlib's units registry
  to plot such values as datetimes. This is activated once pandas is imported. In
  previous versions, plotting an array of ``datetime64`` values will have resulted
  in plotted integer values. To keep the previous behaviour, you can do
  ``del matplotlib.units.registry[np.datetime64]`` (:issue:`8614`).


.. _whatsnew_0151.enhancements:

Enhancements
~~~~~~~~~~~~

- Added option to select columns when importing Stata files (:issue:`7935`)
- Qualify memory usage in ``DataFrame.info()`` by adding ``+`` if it is a lower bound (:issue:`8578`)
- Raise errors in certain aggregation cases where an argument such as ``numeric_only`` is not handled (:issue:`8592`).


- Added support for 3-character ISO and non-standard country codes in :func:``io.wb.download()`` (:issue:`8482`)
- :ref:`World Bank data requests <remote_data.wb>` now will warn/raise based on an ``errors`` argument, as well as a list of hard-coded country codes and the World Bank's JSON response.  In prior versions, the error messages didn't look at the World Bank's JSON response.  Problem-inducing input were simply dropped prior to the request.  The issue was that many good countries were cropped in the hard-coded approach.  All countries will work now, but some bad countries will raise exceptions because some edge cases break the entire response. (:issue:`8482`)
- Added option to ``Series.str.split()`` to return a ``DataFrame`` rather than a ``Series`` (:issue:`8428`)
- Added option to ``df.info(null_counts=None|True|False)`` to override the default display options and force showing of the null-counts (:issue:`8701`)

Bug Fixes
~~~~~~~~~

- Bug in unpickling  of a ``CustomBusinessDay`` object (:issue:`8591`)
- Bug in coercing ``Categorical`` to a records array, e.g. ``df.to_records()`` (:issue:`8626`)
- Bug in ``Categorical`` not created properly with ``Series.to_frame()`` (:issue:`8626`)
- Bug in coercing in astype of a ``Categorical`` of a passed ``pd.Categorical`` (this now raises ``TypeError`` correctly), (:issue:`8626`)
- Bug in ``cut``/``qcut`` when using ``Series`` and ``retbins=True`` (:issue:`8589`)
- Bug in writing Categorical columns to an SQL database with ``to_sql`` (:issue:`8624`).
- Bug in comparing ``Categorical`` of datetime raising when being compared to a scalar datetime (:issue:`8687`)
- Bug in selecting from a ``Categorical`` with ``.iloc`` (:issue:`8623`)
- Bug in groupby-transform with a Categorical (:issue:`8623`)
- Bug in duplicated/drop_duplicates with a Categorical (:issue:`8623`)
- Bug in ``Categorical`` reflected comparison operator raising if the first argument was a numpy array scalar (e.g. np.int64) (:issue:`8658`)
- Bug in Panel indexing with a list-like (:issue:`8710`)
- Compat issue is ``DataFrame.dtypes`` when ``options.mode.use_inf_as_null`` is True (:issue:`8722`)
- Bug in ``read_csv``, ``dialect`` parameter would not take a string (:issue: `8703`)
- Bug in slicing a multi-index level with an empty-list (:issue:`8737`)





- Bug in numeric index operations of add/sub with Float/Index Index with numpy arrays (:issue:`8608`)
- Bug in setitem with empty indexer and unwanted coercion of dtypes (:issue:`8669`)







- Bug in ix/loc block splitting on setitem (manifests with integer-like dtypes, e.g. datetime64) (:issue:`8607`)


- Bug when doing label based indexing with integers not found in the index for
  non-unique but monotonic indexes (:issue:`8680`).
- Bug when indexing a Float64Index with ``np.nan`` on numpy 1.7 (:issue:`8980`).










- Fix ``shape`` attribute for ``MultiIndex`` (:issue:`8609`)
- Bug in ``GroupBy`` where a name conflict between the grouper and columns
  would break ``groupby`` operations (:issue:`7115`, :issue:`8112`)



- Fixed a bug where plotting a column ``y`` and specifying a label would mutate the index name of the original DataFrame (:issue:`8494`)
- Fix regression in plotting of a DatetimeIndex directly with matplotlib (:issue:`8614`).

- Bug in ``date_range`` where partially-specified dates would incorporate current date (:issue:`6961`)

- Bug in Setting by indexer to a scalar value with a mixed-dtype `Panel4d` was failing (:issue:`8702`)

- Bug where ``DataReader``'s would fail if one of the symbols passed was invalid.  Now returns data for valid symbols and np.nan for invalid (:issue:`8494`)
- Bug in ``get_quote_yahoo`` that wouldn't allow non-float return values (:issue:`5229`).
