Seasonal Average Formula

The formula given in this sheet of how SA is calculated is a bit difficult to understand.

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#### Document Details

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* ID: 5d7f02f2-18b1-3558-773c-5b03e7ff5e68
* Version Independent ID: 4cbf1b06-13fe-fd6f-0ba8-3dc1fb0e65e2
* Content: [azureml.automl.runtime.shared.forecasting_models.SeasonalAverage class - Azure Machine Learning Python](https://docs.microsoft.com/en-us/python/api/azureml-automl-runtime/azureml.automl.runtime.shared.forecasting_models.seasonalaverage?view=azure-ml-py)
* Content Source: [AzureML-Docset/stable/docs-ref-autogen/azureml-automl-runtime/azureml.automl.runtime.shared.forecasting_models.SeasonalAverage.yml](https://github.com/MicrosoftDocs/MachineLearning-Python-pr/blob/live/AzureML-Docset/stable/docs-ref-autogen/azureml-automl-runtime/azureml.automl.runtime.shared.forecasting_models.SeasonalAverage.yml)
* Service: **machine-learning**
* Sub-service: **core**
* GitHub Login: @DebFro
* Microsoft Alias: **debfro**

開啟 AzureML-Docset/stable/docs-ref-autogen/azureml-automl-runtime/azureml.automl.runtime.shared.forecasting_models.SeasonalAverage.yml，並對照連結的 SeasonalAverage API 頁面檢查 Seasonal Average 公式。釐清 SA 的計算方式；當產生的文件以易於理解的方式呈現該公式時即完成。

由索引模型根據 Issue 內容生成。