[PDB_prepare.R] Optimize helper function MINMAX_normalisation_func;

[discoleo]

Helper function MINMAX_normalisation_func

The range (min, max) is computed multiple times. It should be computed only once. One of the following conditions also seems redundant: (r[1] == 0) && (r[2] == 0)), as min == max.

Also, inserting a space between "#" and the comments greatly increases readability.

### Helper functions for the analysis

# MIN-MAX normalisation based on the input array
MINMAX_normalisation_func = function(array) {
	# input = numeric array;
	# returns normalised array values;
	
	# check for cases where all B-factor values are 0;
	r = range(array);
	if((r[2] - r[1] == 0) && (r[1] == 0) && (r[2] == 0)) { return (0); }
	
	return ((array - r[1]) / (r[2] - r[1]));
}