one-hot

One hot encode vectors using a streaming implementation.

Note: This was only tested using iojs and uses the Simplified Constructor API

See Wikipedia https://en.wikipedia.org/wiki/One-hot

var OneHot = require('one-hot');

var oneHot = new OneHot(opts)

Instantiate a new instance of OneHot.

opts is an optional object where:

• opts.oneCold = true will use 0 as the hot value and 1 as the cold value. Default: false, ie. 1 is hot and 0 is cold.
• opts.ignoreColumns is an optional array of columns to ignore (by index) when encoding the input vectors

Example

See tests folder for more examples...

var testIVs = [
  [0, 1, 2, 'a', 3],
  [3, 4, 5, 'b', 6],
  [6, 7, 8, 'c', 9]
];

var oneHot = new OneHot();
oneHot.analyze(testIVs, function(err) {
  if (err) throw err;

  oneHot.encode(testIVs, function(err, encodedData) {
    if (err) throw err;

    // print out the encoded input vectors
    console.log(encodedData);
  });
});

Streaming methods

These are the streaming methods. See test directory for an example.

var writeStreamAnalyze = oneHot.analyze()

This must be called with a single pass over all the data to determine how to one hot encode the data.

var writeStreamEncode = oneHot.encode()

This method will one hot encode each input vector via stream transform. Call this method after oneHot.analyze() has completed.

Non-Streaming methods

These are the non-streaming methods.

oneHot.analyze(data, cb)

This must be called with a single pass over all the data to determine how to one hot encode the data. data must be an array of input vectors and cb must be a callback.

oneHot.encode(data, opts, cb)

This method will one hot encode each input vector in data. data must be an array of input vectors and cb must be a callback with a signature of (err, encodedData) where encodedData will be all the one hot encoded data. Call this method after oneHot.analyze() has completed.

opts is an optional object that may include:

• opts.ignoreColumns - an optional array of columns to ignore (by index) when encoding the input vectors. This will override opts.ignoreColumns from the OneHot instantiation.

Methods

var columnsHeader = oneHot.getColumnsHeader(originalColumns)

This method will return an array of the column names. If originalColumns is provided, it will be used to fill in the column names. When originalColumns is undefined, the column names will be null and the one hot features will be <original_column_number:feature_value>. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
var originalColumns = ['one', 'two', 'three', 'char'];
... // removed for brevity (see tests)
oneHot.getColumnsHeader(originalColumns); // ['one', 'two', 'three', 'char:a', 'char:b']
oneHot.getColumnsHeader(); // [null, null, null, '3:a', '3:b']

var numOriginal = oneHot.getNumberOfOriginalFeatures()

This method will return the number of original features. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
oneHot.getNumberOfOriginalFeatures(originalColumns); // 4 {1, 2, 3, 'a'}

var numEncoded = oneHot.getNumberOfEncodedFeatures()

This method will return the number of original features. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
oneHot.getNumberOfEncodedFeatures(originalColumns); // 5, 3 non one hot + 2 one hot {1, 2, 3, 'a', 'b'}

var numEncoded = oneHot.getNumberOfNonEncodedFeatures()

This method will return the number of original features. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
oneHot.getNumberOfNonEncodedFeatures(originalColumns); // 3, {1, 2, 3}

var encodedIndex = oneHot.getEncodedIndexFromOriginalIndex(originalIndex, featureValue)

This method will return the new index (the hot index) of a given original index and it's feature value. You must specify a feature because of the one-to-many relationship between original and encoded. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
var encodedIndex = oneHot.getEncodedIndexFromOriginalIndex(3, 'a'); // encodedIndex could be 3 or 4, [1, 2, 3, 1, 0], or [1, 2, 3, 0, 1] depending on the order in which the ivs were processed

var originalIndex = oneHot.getOriginalIndexFromEncodedIndex(encodedIndex)

This method will return the original index (before encoding) of a given encoded index. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
var originalIndex = oneHot.getOriginalIndexFromEncodedIndex(4); // 3

var internalIndex = oneHot.getInternalIndexFromOriginalIndex(originalIndex, featureValue)

This method will return the index used internally to one hot encode the featureValue, (the hot index) of a given original index and it's feature value. You must specify a feature because of the one-to-many relationship between original and encoded. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
var encodedIndexA = oneHot.getInternalIndexFromOriginalIndex(3, 'a'); // 4, ie, [1, 2, 3, <encoded column: {a, b}>, 1, 0]
var encodedIndexB = oneHot.getInternalIndexFromOriginalIndex(3, 'b'); // 5, ie, [1, 2, 3, <encoded column: {a, b}>, 0, 1]

var originalIndex = oneHot.getOriginalIndexFromInternalIndex(internalIndex)

This method will return the original index from the index used internally to one hot encode. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
var encodedIndexA = oneHot.getOriginalIndexFromInternalIndex(4); // 3, ie, [1, 2, 3, <encoded column: {a, b}>, 1, 0] => [1, 2, 3, 'a']
var encodedIndexB = oneHot.getOriginalIndexFromInternalIndex(5); // 3, ie, [1, 2, 3, <encoded column: {a, b}>, 0, 1] => [1, 2, 3, 'b']

var encodedIndex = oneHot.getEncodedIndexFromInternalIndex(internalIndex)

This method will return the encoded index from the index used internally to one hot encode. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
var encodedIndexA = oneHot.getEncodedIndexFromInternalIndex(4); // 3, ie, [1, 2, 3, <encoded column: {a, b}>, 1, 0] => [1, 2, 3, 1, 0]
var encodedIndexB = oneHot.getEncodedIndexFromInternalIndex(5); // 4, ie, [1, 2, 3, <encoded column: {a, b}>, 0, 1] => [1, 2, 3, 0, 1]

var internalIndex = oneHot.getInternalIndexFromEncodedIndex(encodedIndex)

This method will return the the index used internally to one hot encode from the encoded index. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
var encodedIndexA = oneHot.getInternalIndexFromEncodedIndex(3); // 4, ie, [1, 2, 3, 1, 0] => [1, 2, 3, <encoded column: {a, b}>, 1, 0]
var encodedIndexB = oneHot.getInternalIndexFromEncodedIndex(4); // 5, ie, [1, 2, 3, 0, 1] => [1, 2, 3, <encoded column: {a, b}>, 0, 1]

var isOneHot = oneHot.isEncodedIndexOneHot(encodedIndex)

This method will return true if the encoded index given is a one hot index. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
oneHot.isEncodedIndexOneHot(0); // false
oneHot.isEncodedIndexOneHot(1); // false
oneHot.isEncodedIndexOneHot(2); // false
oneHot.isEncodedIndexOneHot(3); // true

var isOneHot = oneHot.isOriginalIndexOneHot(originalIndex)

This method will return true if the original index given is a one hot index. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
oneHot.isOriginalIndexOneHot(0); // false
oneHot.isOriginalIndexOneHot(1); // false
oneHot.isOriginalIndexOneHot(2); // false
oneHot.isOriginalIndexOneHot(3); // true

var featureValue = oneHot.getFeatureValueFromEncodedIndex(encodedIndex)

This method will return the feature value at a given encoded index. For example:

var oneHot = new OneHot()
var originalIVs = [[1, 2, 3, 'a'], [1, 2, 3, 'b']]
... // removed for brevity (see tests)
oneHot.getFeatureValueFromEncodedIndex(3); // 'a'
oneHot.getFeatureValueFromEncodedIndex(4); // 'b'