.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "auto_examples/applications/plot_time_series_lagged_features.py" .. LINE NUMBERS ARE GIVEN BELOW. .. only:: html .. note:: :class: sphx-glr-download-link-note :ref:`Go to the end ` to download the full example code. or to run this example in your browser via JupyterLite or Binder .. rst-class:: sphx-glr-example-title .. _sphx_glr_auto_examples_applications_plot_time_series_lagged_features.py: =========================================== Lagged features for time series forecasting =========================================== This example demonstrates how Polars-engineered lagged features can be used for time series forecasting with :class:`~sklearn.ensemble.HistGradientBoostingRegressor` on the Bike Sharing Demand dataset. See the example on :ref:`sphx_glr_auto_examples_applications_plot_cyclical_feature_engineering.py` for some data exploration on this dataset and a demo on periodic feature engineering. .. GENERATED FROM PYTHON SOURCE LINES 19-29 Analyzing the Bike Sharing Demand dataset ----------------------------------------- We start by loading the data from the OpenML repository as a pandas dataframe. This will be replaced with Polars once `fetch_openml` adds a native support for it. We convert to Polars for feature engineering, as it automatically caches common subexpressions which are reused in multiple expressions (like `pl.col("count").shift(1)` below). See https://docs.pola.rs/user-guide/lazy/optimizations/ for more information. .. GENERATED FROM PYTHON SOURCE LINES 29-43 .. code-block:: Python import numpy as np import polars as pl from sklearn.datasets import fetch_openml pl.Config.set_fmt_str_lengths(20) bike_sharing = fetch_openml( "Bike_Sharing_Demand", version=2, as_frame=True, parser="pandas" ) df = bike_sharing.frame df = pl.DataFrame({col: df[col].to_numpy() for col in df.columns}) .. GENERATED FROM PYTHON SOURCE LINES 44-46 Next, we take a look at the statistical summary of the dataset so that we can better understand the data that we are working with. .. GENERATED FROM PYTHON SOURCE LINES 46-51 .. code-block:: Python import polars.selectors as cs summary = df.select(cs.numeric()).describe() summary .. raw:: html
shape: (9, 10)
statisticyearmonthhourweekdaytempfeel_temphumiditywindspeedcount
strf64f64f64f64f64f64f64f64f64
"count"17379.017379.017379.017379.017379.017379.017379.017379.017379.0
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"mean"0.5025616.53777511.5467523.00368320.37647423.7887550.62722912.73654189.463088
"std"0.5000083.4387766.9144052.0057717.8948018.5925110.192938.196795181.387599
"min"0.01.00.00.00.820.00.00.01.0
"25%"0.04.06.01.013.9416.6650.487.001540.0
"50%"1.07.012.03.020.524.240.6312.998142.0
"75%"1.010.018.05.027.0631.060.7816.9979281.0
"max"1.012.023.06.041.050.01.056.9969977.0


.. GENERATED FROM PYTHON SOURCE LINES 52-54 Let us look at the count of the seasons `"fall"`, `"spring"`, `"summer"` and `"winter"` present in the dataset to confirm they are balanced. .. GENERATED FROM PYTHON SOURCE LINES 54-60 .. code-block:: Python import matplotlib.pyplot as plt df["season"].value_counts() .. raw:: html
shape: (4, 2)
seasoncount
stru32
"winter"4232
"spring"4242
"fall"4496
"summer"4409


.. GENERATED FROM PYTHON SOURCE LINES 61-68 Generating Polars-engineered lagged features -------------------------------------------- Let's consider the problem of predicting the demand at the next hour given past demands. Since the demand is a continuous variable, one could intuitively use any regression model. However, we do not have the usual `(X_train, y_train)` dataset. Instead, we just have the `y_train` demand data sequentially organized by time. .. GENERATED FROM PYTHON SOURCE LINES 68-84 .. code-block:: Python lagged_df = df.select( "count", *[pl.col("count").shift(i).alias(f"lagged_count_{i}h") for i in [1, 2, 3]], lagged_count_1d=pl.col("count").shift(24), lagged_count_1d_1h=pl.col("count").shift(24 + 1), lagged_count_7d=pl.col("count").shift(7 * 24), lagged_count_7d_1h=pl.col("count").shift(7 * 24 + 1), lagged_mean_24h=pl.col("count").shift(1).rolling_mean(24), lagged_max_24h=pl.col("count").shift(1).rolling_max(24), lagged_min_24h=pl.col("count").shift(1).rolling_min(24), lagged_mean_7d=pl.col("count").shift(1).rolling_mean(7 * 24), lagged_max_7d=pl.col("count").shift(1).rolling_max(7 * 24), lagged_min_7d=pl.col("count").shift(1).rolling_min(7 * 24), ) lagged_df.tail(10) .. raw:: html
shape: (10, 14)
countlagged_count_1hlagged_count_2hlagged_count_3hlagged_count_1dlagged_count_1d_1hlagged_count_7dlagged_count_7d_1hlagged_mean_24hlagged_max_24hlagged_min_24hlagged_mean_7dlagged_max_7dlagged_min_7d
i64i64i64i64i64i64i64i64f64i64i64f64i64i64
2472032241571601697013593.5224167.7321432711
315247203224138160467097.125247168.7857142711
2143152472031331383346104.5315170.3869053151
1642143152471231333333107.875315171.4642863151
1221642143151251232633109.583333315172.2440483151
1191221642141021252626109.458333315172.8154763151
89119122164721021826110.166667315173.3690483151
908911912247722318110.875315173.7916673151
61908911936472223112.666667315174.1904763151
4961908949361222113.708333315174.4226193151


.. GENERATED FROM PYTHON SOURCE LINES 85-87 Watch out however, the first lines have undefined values because their own past is unknown. This depends on how much lag we used: .. GENERATED FROM PYTHON SOURCE LINES 87-89 .. code-block:: Python lagged_df.head(10) .. raw:: html
shape: (10, 14)
countlagged_count_1hlagged_count_2hlagged_count_3hlagged_count_1dlagged_count_1d_1hlagged_count_7dlagged_count_7d_1hlagged_mean_24hlagged_max_24hlagged_min_24hlagged_mean_7dlagged_max_7dlagged_min_7d
i64i64i64i64i64i64i64i64f64i64i64f64i64i64
16nullnullnullnullnullnullnullnullnullnullnullnullnull
4016nullnullnullnullnullnullnullnullnullnullnullnull
324016nullnullnullnullnullnullnullnullnullnullnull
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8321nullnullnullnullnullnullnullnullnullnull
14832nullnullnullnullnullnullnullnullnullnull


.. GENERATED FROM PYTHON SOURCE LINES 90-92 We can now separate the lagged features in a matrix `X` and the target variable (the counts to predict) in an array of the same first dimension `y`. .. GENERATED FROM PYTHON SOURCE LINES 92-97 .. code-block:: Python lagged_df = lagged_df.drop_nulls() X = lagged_df.drop("count") y = lagged_df["count"] print("X shape: {}\ny shape: {}".format(X.shape, y.shape)) .. rst-class:: sphx-glr-script-out .. code-block:: none X shape: (17210, 13) y shape: (17210,) .. GENERATED FROM PYTHON SOURCE LINES 98-108 Naive evaluation of the next hour bike demand regression -------------------------------------------------------- Let's randomly split our tabularized dataset to train a gradient boosting regression tree (GBRT) model and evaluate it using Mean Absolute Percentage Error (MAPE). If our model is aimed at forecasting (i.e., predicting future data from past data), we should not use training data that are ulterior to the testing data. In time series machine learning the "i.i.d" (independent and identically distributed) assumption does not hold true as the data points are not independent and have a temporal relationship. .. GENERATED FROM PYTHON SOURCE LINES 108-117 .. code-block:: Python from sklearn.ensemble import HistGradientBoostingRegressor from sklearn.model_selection import train_test_split X_train, X_test, y_train, y_test = train_test_split( X, y, test_size=0.2, random_state=42 ) model = HistGradientBoostingRegressor().fit(X_train, y_train) .. GENERATED FROM PYTHON SOURCE LINES 118-119 Taking a look at the performance of the model. .. GENERATED FROM PYTHON SOURCE LINES 119-124 .. code-block:: Python from sklearn.metrics import mean_absolute_percentage_error y_pred = model.predict(X_test) mean_absolute_percentage_error(y_test, y_pred) .. rst-class:: sphx-glr-script-out .. code-block:: none 0.3889873516666431 .. GENERATED FROM PYTHON SOURCE LINES 125-131 Proper next hour forecasting evaluation --------------------------------------- Let's use a proper evaluation splitting strategies that takes into account the temporal structure of the dataset to evaluate our model's ability to predict data points in the future (to avoid cheating by reading values from the lagged features in the training set). .. GENERATED FROM PYTHON SOURCE LINES 131-141 .. code-block:: Python from sklearn.model_selection import TimeSeriesSplit ts_cv = TimeSeriesSplit( n_splits=3, # to keep the notebook fast enough on common laptops gap=48, # 2 days data gap between train and test max_train_size=10000, # keep train sets of comparable sizes test_size=3000, # for 2 or 3 digits of precision in scores ) all_splits = list(ts_cv.split(X, y)) .. GENERATED FROM PYTHON SOURCE LINES 142-143 Training the model and evaluating its performance based on MAPE. .. GENERATED FROM PYTHON SOURCE LINES 143-151 .. code-block:: Python train_idx, test_idx = all_splits[0] X_train, X_test = X[train_idx, :], X[test_idx, :] y_train, y_test = y[train_idx], y[test_idx] model = HistGradientBoostingRegressor().fit(X_train, y_train) y_pred = model.predict(X_test) mean_absolute_percentage_error(y_test, y_pred) .. rst-class:: sphx-glr-script-out .. code-block:: none 0.44300751539296973 .. GENERATED FROM PYTHON SOURCE LINES 152-157 The generalization error measured via a shuffled trained test split is too optimistic. The generalization via a time-based split is likely to be more representative of the true performance of the regression model. Let's assess this variability of our error evaluation with proper cross-validation: .. GENERATED FROM PYTHON SOURCE LINES 157-164 .. code-block:: Python from sklearn.model_selection import cross_val_score cv_mape_scores = -cross_val_score( model, X, y, cv=ts_cv, scoring="neg_mean_absolute_percentage_error" ) cv_mape_scores .. rst-class:: sphx-glr-script-out .. code-block:: none array([0.44300752, 0.27772182, 0.3697178 ]) .. GENERATED FROM PYTHON SOURCE LINES 165-168 The variability across splits is quite large! In a real life setting it would be advised to use more splits to better assess the variability. Let's report the mean CV scores and their standard deviation from now on. .. GENERATED FROM PYTHON SOURCE LINES 168-170 .. code-block:: Python print(f"CV MAPE: {cv_mape_scores.mean():.3f} ± {cv_mape_scores.std():.3f}") .. rst-class:: sphx-glr-script-out .. code-block:: none CV MAPE: 0.363 ± 0.068 .. GENERATED FROM PYTHON SOURCE LINES 171-173 We can compute several combinations of evaluation metrics and loss functions, which are reported a bit below. .. GENERATED FROM PYTHON SOURCE LINES 173-223 .. code-block:: Python from collections import defaultdict from sklearn.metrics import ( make_scorer, mean_absolute_error, mean_pinball_loss, root_mean_squared_error, ) from sklearn.model_selection import cross_validate def consolidate_scores(cv_results, scores, metric): if metric == "MAPE": scores[metric].append(f"{value.mean():.2f} ± {value.std():.2f}") else: scores[metric].append(f"{value.mean():.1f} ± {value.std():.1f}") return scores scoring = { "MAPE": make_scorer(mean_absolute_percentage_error), "RMSE": make_scorer(root_mean_squared_error), "MAE": make_scorer(mean_absolute_error), "pinball_loss_05": make_scorer(mean_pinball_loss, alpha=0.05), "pinball_loss_50": make_scorer(mean_pinball_loss, alpha=0.50), "pinball_loss_95": make_scorer(mean_pinball_loss, alpha=0.95), } loss_functions = ["squared_error", "poisson", "absolute_error"] scores = defaultdict(list) for loss_func in loss_functions: model = HistGradientBoostingRegressor(loss=loss_func) cv_results = cross_validate( model, X, y, cv=ts_cv, scoring=scoring, n_jobs=2, ) time = cv_results["fit_time"] scores["loss"].append(loss_func) scores["fit_time"].append(f"{time.mean():.2f} ± {time.std():.2f} s") for key, value in cv_results.items(): if key.startswith("test_"): metric = key.split("test_")[1] scores = consolidate_scores(cv_results, scores, metric) .. GENERATED FROM PYTHON SOURCE LINES 224-240 Modeling predictive uncertainty via quantile regression ------------------------------------------------------- Instead of modeling the expected value of the distribution of :math:`Y|X` like the least squares and Poisson losses do, one could try to estimate quantiles of the conditional distribution. :math:`Y|X=x_i` is expected to be a random variable for a given data point :math:`x_i` because we expect that the number of rentals cannot be 100% accurately predicted from the features. It can be influenced by other variables not properly captured by the existing lagged features. For instance whether or not it will rain in the next hour cannot be fully anticipated from the past hours bike rental data. This is what we call aleatoric uncertainty. Quantile regression makes it possible to give a finer description of that distribution without making strong assumptions on its shape. .. GENERATED FROM PYTHON SOURCE LINES 240-265 .. code-block:: Python quantile_list = [0.05, 0.5, 0.95] for quantile in quantile_list: model = HistGradientBoostingRegressor(loss="quantile", quantile=quantile) cv_results = cross_validate( model, X, y, cv=ts_cv, scoring=scoring, n_jobs=2, ) time = cv_results["fit_time"] scores["fit_time"].append(f"{time.mean():.2f} ± {time.std():.2f} s") scores["loss"].append(f"quantile {int(quantile*100)}") for key, value in cv_results.items(): if key.startswith("test_"): metric = key.split("test_")[1] scores = consolidate_scores(cv_results, scores, metric) scores_df = pl.DataFrame(scores) scores_df .. raw:: html
shape: (6, 8)
lossfit_timeMAPERMSEMAEpinball_loss_05pinball_loss_50pinball_loss_95
strstrstrstrstrstrstrstr
"squared_error""0.30 ± 0.00 s""0.36 ± 0.07""62.3 ± 3.5""39.1 ± 2.3""17.7 ± 1.3""19.5 ± 1.1""21.4 ± 2.4"
"poisson""0.33 ± 0.01 s""0.32 ± 0.07""64.2 ± 4.0""39.3 ± 2.8""16.7 ± 1.5""19.7 ± 1.4""22.6 ± 3.0"
"absolute_error""0.41 ± 0.01 s""0.32 ± 0.06""64.6 ± 3.8""39.9 ± 3.2""17.1 ± 1.1""19.9 ± 1.6""22.7 ± 3.1"
"quantile 5""0.55 ± 0.02 s""0.41 ± 0.01""145.6 ± 20.9""92.5 ± 16.2""5.9 ± 0.9""46.2 ± 8.1""86.6 ± 15.3"
"quantile 50""0.58 ± 0.01 s""0.32 ± 0.06""64.6 ± 3.8""39.9 ± 3.2""17.1 ± 1.1""19.9 ± 1.6""22.7 ± 3.1"
"quantile 95""0.55 ± 0.01 s""1.07 ± 0.27""99.6 ± 8.7""72.0 ± 6.1""62.9 ± 7.4""36.0 ± 3.1""9.1 ± 1.3"


.. GENERATED FROM PYTHON SOURCE LINES 266-267 Let us take a look at the losses that minimise each metric. .. GENERATED FROM PYTHON SOURCE LINES 267-281 .. code-block:: Python def min_arg(col): col_split = pl.col(col).str.split(" ") return pl.arg_sort_by( col_split.list.get(0).cast(pl.Float64), col_split.list.get(2).cast(pl.Float64), ).first() scores_df.select( pl.col("loss").get(min_arg(col_name)).alias(col_name) for col_name in scores_df.columns if col_name != "loss" ) .. raw:: html
shape: (1, 7)
fit_timeMAPERMSEMAEpinball_loss_05pinball_loss_50pinball_loss_95
strstrstrstrstrstrstr
"squared_error""absolute_error""squared_error""squared_error""quantile 5""squared_error""quantile 95"


.. GENERATED FROM PYTHON SOURCE LINES 282-293 Even if the score distributions overlap due to the variance in the dataset, it is true that the average RMSE is lower when `loss="squared_error"`, whereas the average MAPE is lower when `loss="absolute_error"` as expected. That is also the case for the Mean Pinball Loss with the quantiles 5 and 95. The score corresponding to the 50 quantile loss is overlapping with the score obtained by minimizing other loss functions, which is also the case for the MAE. A qualitative look at the predictions ------------------------------------- We can now visualize the performance of the model with regards to the 5th percentile, median and the 95th percentile: .. GENERATED FROM PYTHON SOURCE LINES 293-322 .. code-block:: Python all_splits = list(ts_cv.split(X, y)) train_idx, test_idx = all_splits[0] X_train, X_test = X[train_idx, :], X[test_idx, :] y_train, y_test = y[train_idx], y[test_idx] max_iter = 50 gbrt_mean_poisson = HistGradientBoostingRegressor(loss="poisson", max_iter=max_iter) gbrt_mean_poisson.fit(X_train, y_train) mean_predictions = gbrt_mean_poisson.predict(X_test) gbrt_median = HistGradientBoostingRegressor( loss="quantile", quantile=0.5, max_iter=max_iter ) gbrt_median.fit(X_train, y_train) median_predictions = gbrt_median.predict(X_test) gbrt_percentile_5 = HistGradientBoostingRegressor( loss="quantile", quantile=0.05, max_iter=max_iter ) gbrt_percentile_5.fit(X_train, y_train) percentile_5_predictions = gbrt_percentile_5.predict(X_test) gbrt_percentile_95 = HistGradientBoostingRegressor( loss="quantile", quantile=0.95, max_iter=max_iter ) gbrt_percentile_95.fit(X_train, y_train) percentile_95_predictions = gbrt_percentile_95.predict(X_test) .. GENERATED FROM PYTHON SOURCE LINES 323-324 We can now take a look at the predictions made by the regression models: .. GENERATED FROM PYTHON SOURCE LINES 324-353 .. code-block:: Python last_hours = slice(-96, None) fig, ax = plt.subplots(figsize=(15, 7)) plt.title("Predictions by regression models") ax.plot( y_test[last_hours], "x-", alpha=0.2, label="Actual demand", color="black", ) ax.plot( median_predictions[last_hours], "^-", label="GBRT median", ) ax.plot( mean_predictions[last_hours], "x-", label="GBRT mean (Poisson)", ) ax.fill_between( np.arange(96), percentile_5_predictions[last_hours], percentile_95_predictions[last_hours], alpha=0.3, label="GBRT 90% interval", ) _ = ax.legend() .. image-sg:: /auto_examples/applications/images/sphx_glr_plot_time_series_lagged_features_001.png :alt: Predictions by regression models :srcset: /auto_examples/applications/images/sphx_glr_plot_time_series_lagged_features_001.png :class: sphx-glr-single-img .. GENERATED FROM PYTHON SOURCE LINES 354-375 Here it's interesting to notice that the blue area between the 5% and 95% percentile estimators has a width that varies with the time of the day: - At night, the blue band is much narrower: the pair of models is quite certain that there will be a small number of bike rentals. And furthermore these seem correct in the sense that the actual demand stays in that blue band. - During the day, the blue band is much wider: the uncertainty grows, probably because of the variability of the weather that can have a very large impact, especially on week-ends. - We can also see that during week-days, the commute pattern is still visible in the 5% and 95% estimations. - Finally, it is expected that 10% of the time, the actual demand does not lie between the 5% and 95% percentile estimates. On this test span, the actual demand seems to be higher, especially during the rush hours. It might reveal that our 95% percentile estimator underestimates the demand peaks. This could be be quantitatively confirmed by computing empirical coverage numbers as done in the :ref:`calibration of confidence intervals `. Looking at the performance of non-linear regression models vs the best models: .. GENERATED FROM PYTHON SOURCE LINES 375-402 .. code-block:: Python from sklearn.metrics import PredictionErrorDisplay fig, axes = plt.subplots(ncols=3, figsize=(15, 6), sharey=True) fig.suptitle("Non-linear regression models") predictions = [ median_predictions, percentile_5_predictions, percentile_95_predictions, ] labels = [ "Median", "5th percentile", "95th percentile", ] for ax, pred, label in zip(axes, predictions, labels): PredictionErrorDisplay.from_predictions( y_true=y_test, y_pred=pred, kind="residual_vs_predicted", scatter_kwargs={"alpha": 0.3}, ax=ax, ) ax.set(xlabel="Predicted demand", ylabel="True demand") ax.legend(["Best model", label]) plt.show() .. image-sg:: /auto_examples/applications/images/sphx_glr_plot_time_series_lagged_features_002.png :alt: Non-linear regression models :srcset: /auto_examples/applications/images/sphx_glr_plot_time_series_lagged_features_002.png :class: sphx-glr-single-img .. GENERATED FROM PYTHON SOURCE LINES 403-426 Conclusion ---------- Through this example we explored time series forecasting using lagged features. We compared a naive regression (using the standardized :class:`~sklearn.model_selection.train_test_split`) with a proper time series evaluation strategy using :class:`~sklearn.model_selection.TimeSeriesSplit`. We observed that the model trained using :class:`~sklearn.model_selection.train_test_split`, having a default value of `shuffle` set to `True` produced an overly optimistic Mean Average Percentage Error (MAPE). The results produced from the time-based split better represent the performance of our time-series regression model. We also analyzed the predictive uncertainty of our model via Quantile Regression. Predictions based on the 5th and 95th percentile using `loss="quantile"` provide us with a quantitative estimate of the uncertainty of the forecasts made by our time series regression model. Uncertainty estimation can also be performed using `MAPIE `_, that provides an implementation based on recent work on conformal prediction methods and estimates both aleatoric and epistemic uncertainty at the same time. Furthermore, functionalities provided by `sktime `_ can be used to extend scikit-learn estimators by making use of recursive time series forecasting, that enables dynamic predictions of future values. .. rst-class:: sphx-glr-timing **Total running time of the script:** (0 minutes 9.067 seconds) .. _sphx_glr_download_auto_examples_applications_plot_time_series_lagged_features.py: .. only:: html .. container:: sphx-glr-footer sphx-glr-footer-example .. container:: binder-badge .. image:: images/binder_badge_logo.svg :target: https://mybinder.org/v2/gh/scikit-learn/scikit-learn/main?urlpath=lab/tree/notebooks/auto_examples/applications/plot_time_series_lagged_features.ipynb :alt: Launch binder :width: 150 px .. container:: lite-badge .. image:: images/jupyterlite_badge_logo.svg :target: ../../lite/lab/?path=auto_examples/applications/plot_time_series_lagged_features.ipynb :alt: Launch JupyterLite :width: 150 px .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: plot_time_series_lagged_features.ipynb ` .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: plot_time_series_lagged_features.py ` .. include:: plot_time_series_lagged_features.recommendations .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_