nltk :: probability :: ConditionalFreqDist :: Class ConditionalFreqDist

Class ConditionalFreqDist

object --+
         |
        ConditionalFreqDist

Known Subclasses:

jazzparser.utils.nltk.probability.CutoffConditionalFreqDist

A collection of frequency distributions for a single experiment run under different conditions. Conditional frequency distributions are used to record the number of times each sample occurred, given the condition under which the experiment was run. For example, a conditional frequency distribution could be used to record the frequency of each word (type) in a document, given its length. Formally, a conditional frequency distribution can be defined as a function that maps from each condition to the FreqDist for the experiment under that condition.

The frequency distribution for each condition is accessed using the indexing operator:

>>> cfdist[3]
<FreqDist with 73 outcomes>
>>> cfdist[3].freq('the')
0.4
>>> cfdist[3]['dog']
2

When the indexing operator is used to access the frequency distribution for a condition that has not been accessed before, ConditionalFreqDist creates a new empty FreqDist for that condition.

Conditional frequency distributions are typically constructed by repeatedly running an experiment under a variety of conditions, and incrementing the sample outcome counts for the appropriate conditions. For example, the following code will produce a conditional frequency distribution that encodes how often each word type occurs, given the length of that word type:

>>> cfdist = ConditionalFreqDist()
>>> for word in tokenize.whitespace(sent):
...     condition = len(word)
...     cfdist[condition].inc(word)

An equivalent way to do this is with the initializer:

>>> cfdist = ConditionalFreqDist((len(word), word) for word in tokenize.whitespace(sent))

Instance Methods

[hide private]

int

N(self)
Returns: The total number of sample outcomes that have been recorded by this ConditionalFreqDist.

__eq__(self, other)

__ge__(self, other)

FreqDist

__getitem__(self, condition)
Returns: The frequency distribution that encodes the frequency of each sample outcome, given that the experiment was run under the given condition.

__gt__(self, other)

__init__(self, cond_samples=None)
Construct a new empty conditional frequency distribution.

__le__(self, other)

int

__len__(self)
Returns: The number of conditions that have been accessed for this ConditionalFreqDist.

__lt__(self, other)

__ne__(self, other)

string

__repr__(self)
Returns: A string representation of this ConditionalFreqDist.

list

conditions(self)
Returns: A list of the conditions that have been accessed for this ConditionalFreqDist.

plot(self, *args, **kwargs)
Plot the given samples from the conditional frequency distribution.

tabulate(self, *args, **kwargs)
Tabulate the given samples from the conditional frequency distribution.

Inherited from object: __delattr__, __format__, __getattribute__, __hash__, __new__, __reduce__, __reduce_ex__, __setattr__, __sizeof__, __str__, __subclasshook__

Properties

[hide private]

Inherited from object: __class__

Method Details

[hide private]

N(self)

Returns: int: The total number of sample outcomes that have been recorded by this ConditionalFreqDist.

getitem(self, condition)
(Indexing operator)

Parameters:

condition (any) - The condition under which the experiment was run.

Returns: FreqDist

The frequency distribution that encodes the frequency of each sample outcome, given that the experiment was run under the given condition. If the frequency distribution for the given condition has not been accessed before, then this will create a new empty FreqDist for that condition.

init(self, cond_samples=None)
(Constructor)

Construct a new empty conditional frequency distribution. In particular, the count for every sample, under every condition, is zero.

Parameters:

cond_samples (Sequence of (condition, sample) tuples) - The samples to initialize the conditional frequency distribution with

Overrides: object.__init__

len(self)
(Length operator)

Returns: int: The number of conditions that have been accessed for this ConditionalFreqDist.

repr(self)
(Representation operator)

repr(x)

Returns: string: A string representation of this ConditionalFreqDist.
Overrides: object.__repr__

conditions(self)

Returns: list: A list of the conditions that have been accessed for this ConditionalFreqDist. Use the indexing operator to access the frequency distribution for a given condition. Note that the frequency distributions for some conditions may contain zero sample outcomes.

plot(self, *args, **kwargs)

Plot the given samples from the conditional frequency distribution. For a cumulative plot, specify cumulative=True. (Requires Matplotlib to be installed.)

Parameters:

samples (list) - The samples to plot
title (str) - The title for the graph
conditions (list) - The conditions to plot (default is all)

tabulate(self, *args, **kwargs)

Tabulate the given samples from the conditional frequency distribution.

Parameters:

samples (list) - The samples to plot
title (str) - The title for the graph
conditions (list) - The conditions to plot (default is all)

Class ConditionalFreqDist

N(self)

__getitem__(self, condition) (Indexing operator)

__init__(self, cond_samples=None) (Constructor)

__len__(self) (Length operator)

__repr__(self) (Representation operator)

conditions(self)

plot(self, *args, **kwargs)

tabulate(self, *args, **kwargs)

getitem(self, condition)
(Indexing operator)

init(self, cond_samples=None)
(Constructor)

len(self)
(Length operator)

repr(self)
(Representation operator)