train_dimensionality_reduction
Train and store a machine learning model to be loaded at a later point for prediction.
Dimensionality reduction with “Uniform Manifold Approximation and Projection” (UMAP)
Generates numeric embeddings (vectors) of the input data with reduced dimensionality, preserving
local and global similarities between data points. Can be used for visualisation, for example,
to arrange data in 2 dimensions according to their similarity, or to create nearest neighbour graphs/networks
(also see step
link_embeddings in the latter case).
Can be used in supervised mode (providing a target column as parameter) or unsupervised (without target).
The output will always be a new column with the trained model’s predictions on the training data,
as well as a saved and named model file that can be used in other projects for prediction of new data.
Usage
The following examples show how the step can be used in a recipe.Examples
Examples
Train an unsupervised UMAP model.
Inputs & Outputs
The following are the inputs expected by the step and the outputs it produces. These are generally columns (ds.first_name), datasets (ds or ds[["first_name", "last_name"]]) or models (referenced
by name e.g. "churn-clf").
Inputs
Inputs
Should contain the target column and the feature columns you wish to use in the model.
Outputs
Outputs
Configuration
The following parameters can be used to configure the behaviour of the step by including them in a json object as the last “input” to the step, i.e.step(..., {"param": "value", ...}) -> (output).
Parameters
Parameters
Target variable.
Name of the column that contains your target values.
Toggle encoding of feature columns.
When enabled, Graphext will auto-convert any column types to the numeric type before
fitting the model. How this conversion is done can be configured using the
feature_encoder
option below.If disabled, any model trained in this step will assume that input data
is already in an appropriate format (e.g. numerical and not containing any missing values).
Configures encoding of feature columns.
By default (
null), Graphext chooses automatically how to convert any column types the model
may not understand natively to a numeric type.A configuration object can be passed instead to overwrite specific parameter values with respect
to their default values.Properties
Properties
Numeric encoder.
Configures encoding of numeric features.
Properties
Properties
Toggle the addition of a column using 0s and 1s to indicate where an input column contained missing values.
Whether and how to impute (replace/fill) missing values.Values must be one of the following:
MeanMedianMostFrequentConstNone
Whether and how to scale the final numerical values (across a single column).Values must be one of the following:
StandardRobustKNNNone
Further parameters passed to the
scaler function.
Details depend no the particular scaler used.Boolean encoder.
Configures encoding of boolean features.
Ordinal encoder.
Configures encoding of categorical features that have a natural order.
Category encoder.
May contain either a single configuration for all categorical variables, or two different configurations
for low- and high-cardinality variables. For further details pick one of the two options below.
Options
Options
Toggle the addition of a column using 0s and 1s to indicate where an input column contained missing values.
Whether and how to impute (replace/fill) missing values.Values must be one of the following:
MostFrequentConstNone
Maximum number of unique categories to encode.
Only the N-1 most common categories will be encoded, and the rest will be grouped into a single
“Others” category.Values must be in the following range:
How to encode categories.Values must be one of the following:
OneHot Label Ordinal Binary Frequency NoneWhether and how to scale the final numerical values (across a single column).Values must be one of the following:
StandardRobustKNNNone
Multilabel encoder.
Configures encoding of multivalued categorical features (variable length lists of categories,
or the semantic type
list[category] for short). May contain either a single configuration for
all multilabel variables, or two different configurations for low- and high-cardinality variables.
For further details pick one of the two options below.Options
Options
Toggle the addition of a column using 0s and 1s to indicate where an input column contained missing values.
How to encode categories/labels in multilabel (list[category]) columns.Values must be one of the following:
BinarizerTfIdfNone
Maximum number of categories/labels to encode.
If a number is provided, the result of the encoding will be reduced to these many dimensions (columns)
using scikit-learn’s truncated SVD.
When applied together with (after a) Tf-Idf encoding, this performs a kind of
latent semantic analysis.Values must be in the following range:
How to scale the encoded (numerical columns).Values must be one of the following:
EuclideanKNNNormNone
Datetime encoder.
Configures encoding of datetime (timestamp) features.
Properties
Properties
Toggle the addition of a column using 0s and 1s to indicate where an input column contained missing values.
A list of numerical components to extract.
Will create one numeric column for each component.
Array items
Array items
Each item in array.Values must be one of the following:
day dayofweek dayofyear hour minute month quarter season second week weekday weekofyear yearA list of cyclical time features to extract.
“Cycles” are numerical transformations of features that should be represented on a circle. E.g. months,
ranging from 1 to 12, should be arranged such that 12 and 1 are next to each other, rather than on
opposite ends of a linear scale. We represent such cyclical time features on a circle by creating two
columns for each original feature: the sin and cos of the numerical feature after appropriate scaling.
Array items
Array items
Each item in array.Values must be one of the following:
daydayofweekdayofyearhourmonth
Whether to include the epoch as new feature (seconds since 01/01/1970).
Whether and how to impute (replace/fill) missing values.Values must be one of the following:
MeanMedianMostFrequentConstNone
Whether and how to scale the final numerical values (across a single column).Values must be one of the following:
StandardRobustKNNNone
How to scale the encoded (numerical columns).Values must be one of the following:
EuclideanKNNNormNone
Embedding/vector encoder.
Configures encoding of multivalued numerical features (variable length lists of numbers, i.e. vectors, or the semantic type
list[number] for short).Text encoder.
Configures encoding of text (natural language) features. Currently only allows
Tf-Idf embeddings to represent texts. If you wish
to use other embeddings, e.g. semantic, Word2Vec etc., transform your text column first using
another step, and then use that result instead of the original texts.
Texts are excluded by default from the overall encoding of the dataset. See parameter
include_text_features below to active it.Properties
Properties
Toggle the addition of a column using 0s and 1s to indicate where an input column contained missing values.
Parameters to be passed to the text encoder (Tf-Idf parameters only for now).
See scikit-learn’s documentation
for detailed parameters and their explanation.
How many output features to generate.
The resulting Tf-Idf vectors will be reduced to these many dimensions (columns) using scikit-learn’s
truncated SVD.
This performs a kind of latent semantic analysis.
By default we will reduce to 200 components.Values must be in the following range:
How to scale the encoded (numerical columns).Values must be one of the following:
EuclideanKNNNormNone
Whether to include or ignore text columns during the processing of input data.
Enabling this will convert texts to their TfIdf representation. Each text will be
converted to an N-dimensional vector in which each component measures the relative
“over-representation” of a specific word (or n-gram) relative to its overall
frequency in the whole dataset. This is disabled by default because it will
often be better to convert texts explicitly using a previous step, such as
embed_text or embed_text_with_model.Model parameters.
See official UMAP documentation for details.
Properties
Properties
Number of neighbors.
This determines the number of neighboring points used in local approximations of manifold structure.
Larger values will result in more global structure being preserved at the loss of detailed local
structure. In general this parameter should often be in the range 5 to 50, with a choice of 10 to 15
being a sensible default.Values must be in the following range:
Minimum distance between reduced data points.
Controls how tightly UMAP is allowed to pack points together in the reduced space. Smaller values will lead to points more tightly
packed together (potentially useful if result is used to cluster the points). Larger values will distribute points with more space
between them (which may be desirable for visualization, or to focus more on the global structure of the date).For further details see here.Values must be in the following range:
Number of n_components.
Allows the user to determine the dimensionality of the reduced dimension space we will be embedding the
data into.Values must be in the following range:
Metric to use for measuring similarity between data points.Values must be one of the following:
euclidean manhattan chebyshev minkowski canberra braycurtis haversine mahalanobis wminkowski seuclidean cosine correlation hamming jaccard dice russellrao kulsinski rogerstanimoto sokalmichener sokalsneath yuleNumber of training iterations used in optimizing the embedding.
Larger values result in more accurate embeddings. If
null is specified a value will be selected based on the size of the input dataset
(200 for large datasets, 500 for small).How to initialize the low dimensional embedding.
When “spectral”, uses a (relatively expensive) spectral embedding. “pca” uses the first
n_components
from a principal component analysis. “tswspectral” is a cheaper alternative to “spectral”. When “random”,
assigns initial embedding positions at random. This uses the least amount of memory and time but may make UMAP
slower to converge on the optimal embedding.Values must be one of the following:spectralpcatswspectralrandom
Avoid excessive memory use.
For some datasets nearest neighbor computations can consume a lot of memory. If you find the step is failing due to memory constraints,
consider setting this option to
true. This approach is more computationally expensive, but avoids excessive memory use.Weighting factor between features and target.
A value of 0.0 weights entirely on data, and a value of 1.0 weights entirely on target. The default of 0.5 balances
the weighting equally between data and target.
Seed for random number generator ensuring reproducibility.Values must be in the following range: