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Description
quantities related
xref #2494
xref #1071
custom meta-data
xref #2485
It would be very convenient if unit support could be integrated into pandas.
Idea: pandas checks for the presence of a unit-attribute of columns and - if present - uses it
- with 'print' to show the units e.g. below the column names
- to calculate 'under the hood' with these units similar to the example below
For my example I use the module pint and add an attribute 'unit' to columns (and a 'title'...).
Example:
from pandas import DataFrame as DF
from pint import UnitRegistry
units = UnitRegistry()
class ColumnDescription():
'''Column description with additional attributes.
The idea is to use this description to be able to add unit and title
attributes to a column description in one step.
A list of ColumnDescriptions is than used as argument to DataFrame()
with unit support.
'''
def __init__(self, name, data, title = None, unit = None):
'''
Args:
name (str): Name of the column..
data (list): List of the column data.
title (str): Title of the column. Defaults to None.
unit (str): Unit of the column (see documentation of module pint).
Defaults to None.
'''
self.data = data
'''(list): List of the column data.'''
self.name = name
'''(str): Name of the column, naming convention similar to python variables.
Used to access the column with pandas syntax, e.g. df['column'] or df.column.
'''
self.title = title
'''(str): Title of the column.
More human readable than the 'name'. E.g.:
Title: 'This is a column title'.
name: 'column_title'.
'''
self.unit = unit
'''Unit of the column (see module pint).
Intended to be used in calculations involving different columns.
'''
class DataFrame(DF):
'''Data Frame with support for ColumnDescriptions (e.g. unit support).
1. See documentation of pandas.DataFrame.
2. When used with ColumnDescriptions supports additional column attributes
like title and unit.
'''
def __init__(self, data, title = None):
'''
Args:
data (list or dict):
1. Dict, as in documentation of DataFrame
2. List of the column data (of type ColumnDescription).
title (str): Title of the data frame. Defaults to None.
'''
if isinstance(data, list):
if isinstance(data[0], ColumnDescription):
d = {}
for column in data:
d[column.name] = column.data
super(DataFrame, self).__init__(d)
for column in data:
self[column.name].title = column.title
self[column.name].unit = column.unit
self.title = title
else:
super(DataFrame, self).__init__(data)
if __name__ == '__main__':
data = [ ColumnDescription('length',
[1, 10],
title = 'Length in meter',
unit = 'meter'),
ColumnDescription('time',
[10, 1],
title = 'Time in s',
unit = 's') ]
d = {'length':[1, 10],
'time': [10, 1]}
df = DataFrame(d)
print 'standard df'
print df
df = DataFrame(data)
print '\n' + 'new df'
print df
####use of dimensions####
# pint works with numpy arrays
# df[name] is currently not working with pint, but would be I think
# it would be a real enhancement if it would...
test = df.as_matrix(['length']) * units(df['length'].unit) / \
(df.as_matrix(['time']) * units(df['time'].unit))
print '\n' + 'unit test'
print test
print '\n' + 'magnitude'
print test.magnitude
print '\n' + 'dimensionality'
print test.dimensionality