preprocessing.clj

(ns scicloj.metamorph.ml.preprocessing
  (:require
   [tablecloth.api :as tc]
   [tech.v3.dataset.math :as std-math]))
   


(defn- preprocessor
  ([columns-selector fit-fn transform-fn context-key options]
   (preprocessor columns-selector :name fit-fn transform-fn context-key options))
  ([columns-selector meta-field fit-fn transform-fn context-key options]

   (fn [{:metamorph/keys [data id mode] :as ctx}]
     (case mode
       :fit
       (let [ds (tc/select-columns data columns-selector meta-field)
             fit-xform (fit-fn ds options)]
         (assoc ctx
                id {context-key fit-xform}
                :metamorph/data (merge data (transform-fn ds fit-xform))))
       :transform
       (assoc ctx :metamorph/data
              (merge data
                     (-> (tc/select-columns data columns-selector meta-field)
                         (transform-fn
                          (get-in ctx [id context-key])))))))))
(defn std-scale
  "Metamorph transfomer, which centers and scales the dataset per column.

  `columns-selector` tablecloth columns-selector to choose columns to work on
  `meta-field` tablecloth meta-field working with `columns-selector`


  `options` are the options for the scaler and can take:
     `mean?` If true (default), the data gets shifted by the column means, so 0 centered
     `stddev?` If true (default), the data gets scaled by the standard deviation of the column

  metamorph                            | .
  -------------------------------------|----------------------------------------------------------------------------
  Behaviour in mode :fit               | Centers and scales the dataset at key `:metamorph/data` and stores the trained model in ctx under key at `:metamorph/id`
  Behaviour in mode :transform         | Reads trained std-scale model from ctx and applies it to data in `:metamorph/data`
  Reads keys from ctx                  | In mode `:transform` : Reads trained model to use for from key in `:metamorph/id`.
  Writes keys to ctx                   | In mode `:fit` : Stores trained model in key $id

  "
  ([columns-selector meta-field {:keys [mean? stddev?]
                                 :or {mean? true stddev? true}
                                 :as options}]
   (preprocessor columns-selector  meta-field std-math/fit-std-scale std-math/transform-std-scale :fit-std-xform options))
  ([columns-selector options] (std-scale columns-selector :name options)))

(defn min-max-scale
  "Metamorph transfomer, which scales the column data into a given range.

  `columns-selector` tablecloth columns-selector to choose columns to work on
  `meta-field` tablecloth meta-field working with `columns-selector`

  `options` Options for scaler, can take:
      `min` Minimal value to scale to (default -0.5)
      `max` Maximum value to scale to (default 0.5)

  metamorph                            | .
  -------------------------------------|----------------------------------------------------------------------------
  Behaviour in mode :fit               | Scales the dataset at key `:metamorph/data` and stores the trained model in ctx under key at `:metamorph/id`
  Behaviour in mode :transform         | Reads trained min-max-scale model from ctx and applies it to data in `:metamorph/data`
  Reads keys from ctx                  | In mode `:transform` : Reads trained model to use for from key in `:metamorph/id`.
  Writes keys to ctx                   | In mode `:fit` : Stores trained model in key $id

  "
  [columns-selector {:keys [min max]
                     :or {min -0.5
                          max 0.5}
                     :as options}]
  (preprocessor columns-selector std-math/fit-minmax std-math/transform-minmax :fit-minmax-xform options))