Add scaling strategies

frontend/normstrategy.py

@@ -0,0 +1,138 @@
+from abc import ABC, abstractmethod
+from pandas import DataFrame, Series
+from pandas.api.types import is_numeric_dtype
+from typing import Any, Union
+
+class DataFrameFunction(ABC):
+    """A command that may be applied in-place to a dataframe."""
+
+    @abstractmethod
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        """Apply the current function to the given dataframe, in-place.
+
+        The series is described by its label and dataframe."""
+        return df
+
+
+class MVStrategy(DataFrameFunction):
+    """A way to handle missing values in a dataframe."""
+
+    @staticmethod
+    def list_available(df: DataFrame, series: Series) -> list['MVStrategy']:
+        """Get all the strategies that can be used."""
+        choices = [DropStrategy(), ModeStrategy()]
+        if is_numeric_dtype(series):
+            choices.extend((MeanStrategy(), MedianStrategy(), LinearRegressionStrategy()))
+        return choices
+
+
+class ScalingStrategy(DataFrameFunction):
+    """A way to handle missing values in a dataframe."""
+
+    @staticmethod
+    def list_available(df: DataFrame, series: Series) -> list['MVStrategy']:
+        """Get all the strategies that can be used."""
+        choices = [KeepStrategy()]
+        if is_numeric_dtype(series):
+            choices.extend((MinMaxStrategy(), ZScoreStrategy()))
+            if series.sum() != 0:
+                choices.append(UnitLengthStrategy())
+        return choices
+
+
+class DropStrategy(MVStrategy):
+    #@typing.override
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        df.dropna(subset=label, inplace=True)
+        return df
+
+    def __str__(self) -> str:
+        return "Drop"
+
+
+class PositionStrategy(MVStrategy):
+    #@typing.override
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        series.fillna(self.get_value(series), inplace=True)
+        return df
+
+    @abstractmethod
+    def get_value(self, series: Series) -> Any:
+        pass
+
+
+class MeanStrategy(PositionStrategy):
+    #@typing.override
+    def get_value(self, series: Series) -> Union[int, float]:
+        return series.mean()
+
+    def __str__(self) -> str:
+        return "Use mean"
+
+
+class MedianStrategy(PositionStrategy):
+    #@typing.override
+    def get_value(self, series: Series) -> Union[int, float]:
+        return series.median()
+
+    def __str__(self) -> str:
+        return "Use median"
+
+
+class ModeStrategy(PositionStrategy):
+    #@typing.override
+    def get_value(self, series: Series) -> Any:
+        return series.mode()[0]
+
+    def __str__(self) -> str:
+        return "Use mode"
+
+
+class LinearRegressionStrategy(MVStrategy):
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        series.interpolate(inplace=True)
+        return df
+
+    def __str__(self) -> str:
+        return "Use linear regression"
+
+
+class KeepStrategy(ScalingStrategy):
+    #@typing.override
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        return df
+
+    def __str__(self) -> str:
+        return "No-op"
+
+
+class MinMaxStrategy(ScalingStrategy):
+    #@typing.override
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        minimum = series.min()
+        maximum = series.max()
+        df[label] = (series - minimum) / (maximum - minimum)
+        return df
+
+    def __str__(self) -> str:
+        return "Min-max"
+
+
+class ZScoreStrategy(ScalingStrategy):
+    #@typing.override
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        df[label] = (series - series.mean()) / series.std()
+        return df
+
+    def __str__(self) -> str:
+        return "Z-Score"
+
+
+class UnitLengthStrategy(ScalingStrategy):
+    #@typing.override
+    def apply(self, df: DataFrame, label: str, series: Series) -> DataFrame:
+        df[label] = series / series.sum()
+        return df
+
+    def __str__(self) -> str:
+        return "Unit length"