2.2.3. Theil-Sen's Estimator

Theil-Sen slope estimate method were used to analyse the long-term trend in the data and the seasonality. The Theil-Sen estimator (TSE) is fairly resistant to outliers and is robust with a high breakdown point of 29.3% [37,38]. TSE method was first outlined by Theil [39] and later expanded upon by Sen [40]. The determination of trend slope of n-pair of data is given by the formula:

$$T\_i = \frac{x\_j - x\_i}{j - i},\tag{4}$$

where, *xj* and *xi* presents as data values at time *j* and *i* (*j* > *i*) respectively [37].
