Estimation of Missing Rainfall Data Using GEP: Case Study of Raja River, Alor Setar, Kedah

Table 2

Functional set for the GEP model.

Function Set	Symbol	Weight	Arity
Addition	+	2	2
Subtraction	−	2	2
Multiplication	*	2	2
Division	/	1	2
Square root	sqrt	1	1
Exponential	exp	1	1
Natural logarithm	ln	1	1
to the power of 2	2	1	1
to the power of 3	3	1	1
Sine	sin	1	1
Cosine	cos	1	1
Tangent	tan	1	1