KoalaTransforms

Common data transformations performed in machine learning, for use with the Koala environment.

Installation

Refer to the Koala repository.

Quickstart

The objects of a concrete subtype of Transformer store the data-independent hyperparameters describing some transformation. These objects are called transformers. For example, a UnivariateDiscretizer <: Transfomer object stores the number of classes (levels) to discretize some vector:

julia> using KoalaTransforms
julia> t = UnivariateDiscretizer()
UnivariateDiscretizer@...952: 

key or field	value
n_classes	512

julia> t.n_classes = 1000

The objects that do the actual transforming are TransformerMachine objects. These are instantiated by providing the transformer with data:

julia> v = rand(100);
julia> tM = Machine(t, v)
TransformerMachine{UnivariateDiscretizer}@...930:

key or field	value
scheme	object of type KoalaTransforms.UnivariateDiscretizerScheme
transformer	UnivariateDiscretizer@...510

transformer detail: UnivariateDiscretizer@...510:

key or field	value
n_classes	1000

scheme detail: UnivariateDiscretizerScheme@...904:

key or field	value
even_quantiles	[0.00333486, 0.00365538, 0.00397589, 0.0042964, 0.00461692, 0.00493743, 0.00525794, 0.00557846, 0.00589897, 0.00621948 … 0.983008, 0.984141, 0.985274, 0.986408, 0.987541, 0.988674, 0.989808, 0.990941, 0.992074, 0.993208]
odd_quantiles	[0.00349512, 0.00381563, 0.00413615, 0.00445666, 0.00477717, 0.00509769, 0.0054182, 0.00573871, 0.00605923, 0.00637974 … 0.982441, 0.983574, 0.984708, 0.985841, 0.986974, 0.988108, 0.989241, 0.990374, 0.991508, 0.992641]

We can now transform any scalar:

julia> transform(tM, 0.51)
541

Or vector:

julia> w = [0.0, 0.2, 0.4, 0.6, 0.8, 1.0];
julia> w_discrete = transform(tM, w)
6-element Array{Int64,1}:
    1
  167
  409
  607
  786
 1000

Transformations can be inverted if inverse_transform is implemented:

julia> inverse_transform(tM, w_discrete)
6-element Array{Float64,1}:
 0.003334863432704751
 0.1999601745313676
 0.4010114211975037
 0.5999763117413155
 0.7995624272453655
 0.9932075341405199

To see all the implemented transformers, use subtypes(Koala.Transformer) and query each type's docstring for details. For a template for implementing your own Koala transformers, see here.