MetaCSV 0.0.4

Tools for documentation-aware data reading, writing, and analysis

=======
MetaCSV
=======


.. image:: https://travis-ci.org/delgadom/metacsv.svg?branch=master
:target: https://travis-ci.org/delgadom/metacsv

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:target: https://badge.fury.io/py/metacsv

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``metacsv`` - Tools for documentation-aware data reading, writing, and analysis

See the full documentation at ReadTheDocs_

.. _ReadTheDocs: http://metacsv.rtfd.org

Overview
=========

Read in CSV data with a yaml-compliant header directly into
a ``pandas`` ``Series``, ``DataFrame``, or ``Panel`` or an ``xarray``
``DataArray`` or ``Dataset``.

Data specification
----------------------------

Data can be specified using a yaml-formatted header, with the doc-separation string
above and below the yaml block. Only one yaml block is allowed. If the doc-separation
string is not the first (non-whitespace) line in the file, all of the file's contents
will be interpreted by the csv reader. The yaml data can have arbitrary complexity.

.. code-block:: python

>>> import metacsv, io
>>> doc = io.StringIO('''
---
author: A Person
date: 2000-01-01
variables:
pop:
name: Population
unit: millions
gdp:
name: Product
unit: 2005 $Bn
---
region,year,pop,gdp
USA,2010,309.3,13599.3
USA,2011,311.7,13817.0
CAN,2010,34.0,1240.0
CAN,2011,34.3,1276.7
''')


Special attributes
~~~~~~~~~~~~~~~~~~~~~~~

The ``coords`` and ``variables`` attributes are keywords and are not simply passed
to the MetaCSV object's ``attrs`` attribute.

``variables`` describes columns in the resulting ``DataFrame`` or ``Data variables``
in the resulting ``xarray.Dataset``. Variables is not used when the CSV has only one
column and the argumetn ``squeeze=True`` is passed to ``read_csv``.

``coords`` describes indices in the resulting ``DataFrame``/``Series``, or
``Coordinates`` in the resulting ``xarray.Dataset/xarray.DataArray``. Coordinates
are categorical or independent variables which index the object's ``values``.



Using MetaCSV-formatted files in python
--------------------------------------------

Read MetaCSV-formatted data into python using pandas-like syntax:

.. code-block:: python

>>> metacsv.read_csv(doc, index_col=[0,1])
>>> df
<metacsv.core.containers.DataFrame (4, 2)>
pop gdp
region year
USA 2010 309.3 13599.3
2011 311.7 13817.0
CAN 2010 34.0 1240.0
2011 34.3 1276.7

Coordinates
* region (region) object CAN, USA
* year (year) int64 2010, 2011
Variables
pop
gdp
Attributes
date: 2000-01-01
author: A Person

Exporting MetaCSV data to other formats
-----------------------------------------------

CSV
~~~~~~~~~

A MetaCSV ``Series`` or ``DataFrame`` can be written as a yaml-prefixed CSV using
the same ``to_csv`` syntax as it's ``pandas`` counterpart:

.. code-block:: python

>>> df.attrs['new attribute'] = 'changed in python!'
>>> # includes changes to data, attributes, variables, and coordinates
... df.to_csv('my_new_data.csv')




pandas
~~~~~~~~~~~~~~~

The coordinates and MetaCSV attributes can be easily stripped from a MetaCSV Container:

.. code-block:: python

>>> df.to_pandas()
pop gdp
region year
USA 2010 309.3 13599.3
2011 311.7 13817.0
CAN 2010 34.0 1240.0
2011 34.3 1276.7



xarray/netCDF
~~~~~~~~~~~~~~~

``xarray`` provides a pandas-like interface to operating on indexed ``ndarray`` data. It
is modeled on the ``netCDF`` data storage format used frequently in climate science, but
is useful for many applications with higher-order data.


.. code-block:: python

>>> ds = df.to_xarray()
>>> ds
<xarray.Dataset>
Dimensions: (region: 2, year: 2)
Coordinates:
* region (region) object 'USA' 'CAN'
* year (year) int64 2010 2011
Data variables:
pop (region, year) float64 309.3 311.7 34.0 34.3
gdp (region, year) float64 1.36e+04 1.382e+04 1.24e+03 1.277e+03
Attributes:
date: 2000-01-01
author: A Person
>>> ds.to_netcdf('my_netcdf_data.nc')

Others
~~~~~~~~~

Currently, MetaCSV only supports conversion back to CSV and to
netCDF through the ``xarray`` module. However, feel free to suggest
additional features and to contribute your own!


TODO
============

* Make ``coords`` and ``attrs`` persistent across slicing operations
(try ``df['pop'].to_xarray()`` from above example and watch it
fail...)

* Improve hooks between ``pandas`` and ``metacsv``:

- update ``coord`` names on ``df.index.names`` assignment
- update ``coords`` on stack/unstack
- update ``coords`` on

* Handle attributes indexed by coord/variable names --> assign to
coord/variable-specific ``attrs``

* Let's start an issue tracker and get rid of this section!

* Should we rethink "special attributes," e.g. coords? Maybe these should
have some special prefix like ``_coords`` when included in yaml headers to
avoid confusion with other generic attributes...

* Allow special attributes (``coords``, ``variables``) in ``read_csv`` call

* Allow external file headers

* Write tests

* Write documentation

* Maybe steal xarray's coordinate handling and save ourselves a whole lotta work?


Feature Requests
==================
* Create syntax for ``multi-csv`` --> ``Panel`` or combining using filename regex
* Eventually? allow for on-disk manipulation of many/large files with dask/xarray
* Eventually? add xml, SQL, other structured syntax language conversions



============== ==========================================================
Python support Python 2.7, >= 3.3
Source https://github.com/delgadom/metacsv
Docs http://metacsv.rtfd.org
Changelog http://metacsv.readthedocs.org/en/latest/history.html
API http://metacsv.readthedocs.org/en/latest/api.html
Issues https://github.com/delgadom/metacsv/issues
Travis http://travis-ci.org/delgadom/metacsv
Test coverage https://coveralls.io/r/delgadom/metacsv
pypi https://pypi.python.org/pypi/metacsv
Ohloh https://www.ohloh.net/p/metacsv
License `BSD`_.
git repo .. code-block:: bash

$ git clone https://github.com/delgadom/metacsv.git
install dev .. code-block:: bash

$ git clone https://github.com/delgadom/metacsv.git metacsv
$ cd ./metacsv
$ virtualenv .env
$ source .env/bin/activate
$ pip install -e .
tests .. code-block:: bash

$ python setup.py test
============== ==========================================================

.. _BSD: http://opensource.org/licenses/BSD-3-Clause
.. _Documentation: http://metacsv.readthedocs.org/en/latest/
.. _API: http://metacsv.readthedocs.org/en/latest/api.html


=========
Changelog
=========

Here you can find the recent changes to MetaCSV..

.. changelog::
:version: dev
:released: Ongoing

.. change::
:tags: docs

Updated CHANGES.

.. changelog::
:version: 0.0.1
:released: 2016-05-04

.. change::
:tags: project

First release on PyPi.

.. todo:: vim: set filetype=rst: