Min-max normalization
The min-max normalization strategy was used to compare two or more samples by bringing the data in them to the same scale using the following equation (2):
\(x_{\text{norm}}=\frac{x-x_{\min}}{x_{\max}-x_{\min}}\) (2),
where xnorm is the normalized value in the sample in the range from 0 to 1; x is the real value in the sample;xmin and xmax are the minimum and maximum values in the sample, respectively.