8  Time-series analysis and case forecasting


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This section is ongoing and will form the basis of a separate time-series/forecasting paper.

8.1 bTB case count

8.1.1 Seasonality

Figure 8.1: Seasonality of bTB cases by month.

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8.1.2 STL decomposition

As an initial, exploratory step, we applied a seasonal-trend decomposition procedure based on loess (locally estimated scatterplot smoothing, a type of locally-weighted polynomial regression), abbreviated to STL [9]. The purpose of the decomposition of a time series is to “deconstruct” it into a number of component series which, when combined, will reproduce the original time series. Using STL, the specific aim is to split a seasonal time series into three additive components: the underlying trend, seasonality and the remainder (noise).

Figure 8.2: STL decomposition of bTB cases by month.

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8.1.3 Forecasting cases

Figure 8.3: Forecasting predicitions of monthly bTB cases for 2025.