Trigger

var computeNormalizedValue = {
name: "computeNormalizedValue",
body: function compute() {
var context = getContext();
var collection = context.getCollection();
var currentDocument = context.getRequest().getBody();

var findPreviousDocumentQuery = {
“query”: “SELECT * FROM ROOT WHERE ROOT.EventId2 = @eventId”,
“parameters”: [
	{“name” : “@eventId”, “value” : currentDocument[‘eventId]}
]
}

var queryResult = collection.queryDocuments(
	collection.getSelfLink(),
	findPreviousDocumentQuery,
setNormalizedValue);

function setNormalizedValue(err, documents) {
	if(err) thow new Error(“Error: “ + err.message);

	if(documents.length < 1) {
 //handle no previous document
}
else {
	var previousDocument = documents[0];

	for(i = 0; i < documents.lenght; i++) {
		if(documents[i][‘Date’].getTime() > previousDocument[‘Date’].getTime()) {
			previousDocument = documents[i];
		}
	}

var normalizedValue = currentDocument[‘ClusterizeAttendees’] - previousDocument[‘ClusterizeAttendees’]...

currentDocument[‘NormalizedValue’] = normalizedValue;
}
}
},
triggerType: TriggerType.Pre,
triggerOperation: TriggerOperation.Create
}