# Time Series Forecasting

Time Series Forecasting using SKTime and SKLearn

# Forecasting with SKTime

## Resources

- Overview of time series analysis Python packages
- sktime - A Unified Toolbox for ML with Time Series - Markus Löning | PyData Global 2021
- GitHub SKTime Tutorial

```
# This Python 3 environment comes with many helpful analytics libraries installed
# It is defined by the kaggle/python Docker image: https://github.com/kaggle/docker-python
# For example, here's several helpful packages to load
# Input data files are available in the read-only "../input/" directory
# For example, running this (by clicking run or pressing Shift+Enter) will list all files under the input directory
import os
for dirname, _, filenames in os.walk('/kaggle/input'):
for filename in filenames:
print(os.path.join(dirname, filename))
# You can write up to 20GB to the current directory (/kaggle/working/) that gets preserved as output when you create a version using "Save & Run All"
# You can also write temporary files to /kaggle/temp/, but they won't be saved outside of the current session
```

```
!pip install sktime
!pip install pmdarima
```

```
import numpy as np
import pandas as pd
import seaborn as sns
import sktime as sktime
import matplotlib.pyplot as plt
```

The basic workflow when using SKTime is as follows:

- Specify data
- Specify task
- Specify model
- Fit
- Predict

SKTime also provides some sample datasets and other utilities under the `sktime`

namespace:

```
from sktime.datasets import load_shampoo_sales
from sktime.utils.plotting import plot_series
```

```
df_shampoo = load_shampoo_sales()
plot_series(df_shampoo)
```

```
(<Figure size 1152x288 with 1 Axes>,
, <AxesSubplot:ylabel='Number of shampoo sales'>)
```

```
<Figure size 1152x288 with 1 Axes>
```

## Forecasting

Forecasting works by taking the input data and trying to calculate what the data will be after X time period

This requires us to define a `ForecastingHorizon`

which is the period of time over which we want to predict. `sktime`

also has helpers for these

```
from sktime.forecasting.base import ForecastingHorizon
```

```
# timeframe to predict from
prediction_start = df_shampoo[-6:].index[0]
prediction_range = pd.period_range(prediction_start.start_time, freq=prediction_start.freqstr, periods=6)
prediction_range
```

```
PeriodIndex(['1993-07', '1993-08', '1993-09', '1993-10', '1993-11', '1993-12'], dtype='period[M]')
```

```
fh_shampoo = ForecastingHorizon(
prediction_range,
is_relative=False
)
```

```
train_cutoff = df_shampoo[-6:].index[0]
train_cutoff
```

```
Period('1993-07', 'M')
```

## Train/Test Split

Splitting train and test data can be done by specifying the forecasting horizon, this will return a test set and train set where the test set is in the forecasting horizon

```
from sktime.forecasting.model_selection import temporal_train_test_split
```

```
y_train, y_test = temporal_train_test_split(df_shampoo, fh=fh_shampoo)
```

```
plot_series(y_train, y_test, labels=["y_train", "y_test"])
```

```
(<Figure size 1152x288 with 1 Axes>,
, <AxesSubplot:ylabel='Number of shampoo sales'>)
```

```
<Figure size 1152x288 with 1 Axes>
```

## Forecasting Based on Test/Train Data

This is done similar to `sklearn`

models:

- Instantiate model
- Fit model
- Predict
- Evaluate

To enable this methodology, `sktime`

provides different forecasting models that can be used. Below is an example using a `NaiveForecaster`

:

```
from sktime.forecasting.naive import NaiveForecaster
NaiveForecaster?
```

```
forecaster = NaiveForecaster(strategy="drift", window_length=10)
forecaster.fit(y_train)
```

```
NaiveForecaster(strategy='drift', window_length=10)
```

Once fitted, generate predictions using the `ForecastingHorizon`

that was defined for the prediction period

```
y_pred = forecaster.predict(fh_shampoo)
```

```
plot_series(y_train, y_test, y_pred, labels=["y_train", "y_test", "y_pred"])
```

```
(<Figure size 1152x288 with 1 Axes>,
, <AxesSubplot:ylabel='Number of shampoo sales'>)
```

```
<Figure size 1152x288 with 1 Axes>
```

## Model Evaluation

```
from sktime.performance_metrics.forecasting import mean_absolute_percentage_error
```

```
mean_absolute_percentage_error(y_test, y_pred)
```

```
0.16469764622516225
```

## ARIMA Example

We can also use an ARIMA model for example as follows:

```
from sktime.forecasting.arima import AutoARIMA
```

```
# sp=12 for monthly data seasonality
forecaster = AutoARIMA(sp=12, suppress_warnings=True)
forecaster.fit(y_train)
```

```
AutoARIMA(sp=12, suppress_warnings=True)
```

```
y_pred = forecaster.predict(fh=fh_shampoo)
plot_series(y_train, y_test, y_pred, labels=["y_train", "y_test", "y_pred"])
```

```
(<Figure size 1152x288 with 1 Axes>,
, <AxesSubplot:ylabel='Number of shampoo sales'>)
```

```
<Figure size 1152x288 with 1 Axes>
```

## Using SKLearn Regressors

`sktime`

also supports using `sklearn`

regressors and supports transforming them into time-series compatible regressors by way of the `make_reduction`

function:

```
from sklearn.neighbors import KNeighborsRegressor
from sktime.forecasting.compose import make_reduction
from sktime.datasets import load_airline
airline_df = load_airline()
```

```
y_train, y_test = temporal_train_test_split(airline_df, test_size=12)
plot_series(y_train, y_test, labels=["y_train", "y_test"])
```

```
(<Figure size 1152x288 with 1 Axes>,
, <AxesSubplot:ylabel='Number of airline passengers'>)
```

```
<Figure size 1152x288 with 1 Axes>
```

```
fh = ForecastingHorizon(y_test.index, is_relative=False)
```

transform a regressor into a forecaster

```
regressor = KNeighborsRegressor(n_neighbors=3)
forecaster = make_reduction(regressor, strategy="recursive", window_length=12)
```

```
forecaster.fit(y_train, fh=fh)
```

```
RecursiveTabularRegressionForecaster(estimator=KNeighborsRegressor(n_neighbors=3),
, window_length=12)
```

```
y_pred = forecaster.predict(fh=fh)
plot_series(y_train, y_test, y_pred, labels=["y_train", "y_test", "y_pred"])
```

```
(<Figure size 1152x288 with 1 Axes>,
, <AxesSubplot:ylabel='Number of airline passengers'>)
```

```
<Figure size 1152x288 with 1 Axes>
```

```
```