Rule No.

Range of k

Exponential equation

R2 value

SIF data set

Rule #1

2 ≤ k ≤ 25

R2 = 0.9579

SIF2014

Rule #4

R2 = 0.9705

Rule #5

R2 = 0.9880

Rule #4

4 ≤ k ≤ 20

R2 = 0.9915

SIF2009

R2 = 0.9842

SIF2014

R2 = 0.99

SIF2015

Rule #5

4 ≤ k ≤ 20

R2 = 0.9915

SIF2009

R2 = 0.9951

SIF2014

R2 = 0.9952

SIF2015