Add HorizontalSMAModel

- the model applies a simple moving average on horizontal time series
- refactor `db.Forecast.from_dataframe()` to correctly convert
  `float('NaN')` values into `None`; otherwise, SQLAlchemy complains

setup.cfg

@@ -153,6 +153,9 @@ per-file-ignores =
     src/urban_meal_delivery/forecasts/methods/extrapolate_season.py:
         # The module is not too complex.
         WPS232,
+    src/urban_meal_delivery/forecasts/models/tactical/horizontal.py:
+        # The many noqa's are ok.
+        WPS403,
     src/urban_meal_delivery/forecasts/timify.py:
         # No SQL injection as the inputs come from a safe source.
         S608,

src/urban_meal_delivery/db/forecasts.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import math
 from typing import List
 
 import pandas as pd
@@ -141,7 +142,7 @@ class Forecast(meta.Base):
         )
 
     @classmethod
-    def from_dataframe(  # noqa:WPS211
+    def from_dataframe(  # noqa:WPS210,WPS211
         cls,
         pixel: db.Pixel,
         time_step: int,
@@ -176,20 +177,53 @@ class Forecast(meta.Base):
         forecasts = []
 
         for timestamp_idx in data.index:
-            forecast = cls(
+            start_at = timestamp_idx.to_pydatetime()
+            actual = int(data.loc[timestamp_idx, 'actual'])
+            prediction = round(data.loc[timestamp_idx, 'prediction'], 5)
+
+            # Explicit type casting. SQLAlchemy does not convert
+            # `float('NaN')`s into plain `None`s.
+
+            low80 = data.loc[timestamp_idx, 'low80']
+            high80 = data.loc[timestamp_idx, 'high80']
+            low95 = data.loc[timestamp_idx, 'low95']
+            high95 = data.loc[timestamp_idx, 'high95']
+
+            if math.isnan(low80):
+                low80 = None
+            else:
+                low80 = round(low80, 5)
+
+            if math.isnan(high80):
+                high80 = None
+            else:
+                high80 = round(high80, 5)
+
+            if math.isnan(low95):
+                low95 = None
+            else:
+                low95 = round(low95, 5)
+
+            if math.isnan(high95):
+                high95 = None
+            else:
+                high95 = round(high95, 5)
+
+            forecasts.append(
+                cls(
                     pixel=pixel,
-                start_at=timestamp_idx.to_pydatetime(),
+                    start_at=start_at,
                     time_step=time_step,
                     training_horizon=training_horizon,
                     model=model,
-                actual=int(data.loc[timestamp_idx, 'actual']),
-                prediction=round(data.loc[timestamp_idx, 'prediction'], 5),
-                low80=round(data.loc[timestamp_idx, 'low80'], 5),
-                high80=round(data.loc[timestamp_idx, 'high80'], 5),
-                low95=round(data.loc[timestamp_idx, 'low95'], 5),
-                high95=round(data.loc[timestamp_idx, 'high95'], 5),
+                    actual=actual,
+                    prediction=prediction,
+                    low80=low80,
+                    high80=high80,
+                    low95=low95,
+                    high95=high95,
+                ),
             )
-            forecasts.append(forecast)
 
         return forecasts
 

src/urban_meal_delivery/forecasts/models/__init__.py

@@ -31,5 +31,6 @@ A future `planning` sub-package will contain the `*Model`s used to plan the
 
 from urban_meal_delivery.forecasts.models.base import ForecastingModelABC
 from urban_meal_delivery.forecasts.models.tactical.horizontal import HorizontalETSModel
+from urban_meal_delivery.forecasts.models.tactical.horizontal import HorizontalSMAModel
 from urban_meal_delivery.forecasts.models.tactical.realtime import RealtimeARIMAModel
 from urban_meal_delivery.forecasts.models.tactical.vertical import VerticalARIMAModel

src/urban_meal_delivery/forecasts/models/tactical/horizontal.py

@@ -65,3 +65,66 @@ class HorizontalETSModel(base.ForecastingModelABC):
             raise RuntimeError('missing prediction for `predict_at`')
 
         return predictions
+
+
+class HorizontalSMAModel(base.ForecastingModelABC):
+    """A simple moving average model applied on a horizontal time series."""
+
+    name = 'hsma'
+
+    def predict(
+        self, pixel: db.Pixel, predict_at: dt.datetime, train_horizon: int,
+    ) -> pd.DataFrame:
+        """Predict demand for a time step.
+
+        Args:
+            pixel: pixel in which the prediction is made
+            predict_at: time step (i.e., "start_at") to make the prediction for
+            train_horizon: weeks of historic data used to predict `predict_at`
+
+        Returns:
+            actual order counts (i.e., the "actual" column) and
+                point forecasts (i.e., the "prediction" column);
+                this model does not support confidence intervals;
+                contains one row for the `predict_at` time step
+
+        # noqa:DAR401 RuntimeError
+        """
+        # Generate the historic (and horizontal) order time series.
+        training_ts, frequency, actuals_ts = self._order_history.make_horizontal_ts(
+            pixel_id=pixel.id, predict_at=predict_at, train_horizon=train_horizon,
+        )
+
+        # Sanity checks.
+        if frequency != 7:  # pragma: no cover
+            raise RuntimeError('`frequency` should be `7`')
+        if len(actuals_ts) != 1:  # pragma: no cover
+            raise RuntimeError(
+                'the hsma model can only predict one step into the future',
+            )
+
+        # The "prediction" is calculated as the `np.mean()`.
+        # As the `training_ts` covers only full week horizons,
+        # no adjustment regarding the weekly seasonality is needed.
+        predictions = pd.DataFrame(
+            data={
+                'actual': actuals_ts,
+                'prediction': training_ts.values.mean(),
+                'low80': float('NaN'),
+                'high80': float('NaN'),
+                'low95': float('NaN'),
+                'high95': float('NaN'),
+            },
+            index=actuals_ts.index,
+        )
+
+        # Sanity checks.
+        if (  # noqa:WPS337
+            predictions[['actual', 'prediction']].isnull().any().any()
+        ):  # pragma: no cover
+
+            raise RuntimeError('missing predictions in hsma model')
+        if predict_at not in predictions.index:  # pragma: no cover
+            raise RuntimeError('missing prediction for `predict_at`')
+
+        return predictions

tests/forecasts/test_models.py

@@ -11,6 +11,7 @@ from urban_meal_delivery.forecasts import models
 
 MODELS = (
     models.HorizontalETSModel,
+    models.HorizontalSMAModel,
     models.RealtimeARIMAModel,
     models.VerticalARIMAModel,
 )