normalization function
Implementation
Future normalization(Iterator<MapEntry<String, Node>> nodes) async {
var minNode = await nodes.current.value.getValue('minValue');
var valueNode = await nodes.current.value.getValue('GEIGERvalue');
var maxNode = await nodes.current.value.getValue('maxValue');
var minValue = double.parse(minNode!.getValue('en').toString());
var value = double.parse(valueNode!.getValue('en').toString());
return (value - minValue) /
(double.parse(maxNode!.getValue('en').toString()) - minValue);
}