Custom math with aggregation using mongo and angular - angularjs

Question

I'm currently using aggregation to display registration teams and nets for a stats page. I can do the count on each level, but the calculations for nets is inaccurate. My aggregation is as follows:
module.exports.registrationStats = function(req, res) {
Registration.aggregate([
{
"$group": {
"_id": {
"day": "$day",
"group": "$group",
"division": "$division",
"level": "$level"
},
"count": { "$sum": 1 }
}
},
{
"$group": {
"_id": {
"day": "$_id.day",
"group": "$_id.group",
"division": "$_id.division"
},
"count": { "$sum": "$count" },
"levels": {
"$push": {
"level": "$_id.level",
"teams": "$count",
"nets" : {$ceil : { $divide: [ "$count" , 5 ] } }
}
}
}
},
{
"$group": {
"_id": {
"day": "$_id.day",
"group": "$_id.group"
},
"count": { "$sum": "$count" },
"divisions": {
"$push": {
"division": "$_id.division",
"count": "$count",
"levels": "$levels"
}
}
}
}
]).exec(function(err, regStats){
if(err) {
console.log("Error grouping registrations");
res.status(500).json(err);
} else {
console.log("Found and grouped " + regStats.length + " regStats");
res.json(regStats);
}
});
};
This gives me the following as an output:
[
{
"_id": {
"day": "Saturday",
"group": "nonpro"
},
"count": 144,
"divisions": [
{
"division": "Men's",
"count": 69,
"levels": [
{
"level": "BB",
"teams": 30,
"nets": 6
},
{
"level": "A",
"teams": 8,
"nets": 2
},
{
"level": "B",
"teams": 19,
"nets": 4
},
{
"level": "AA",
"teams": 12,
"nets": 3
}
]
},
{
"division": "Women's",
"count": 75,
"levels": [
{
"level": "AA",
"teams": 9,
"nets": 2
},
{
"level": "BB",
"teams": 16,
"nets": 4
},
{
"level": "B",
"teams": 18,
"nets": 4
},
{
"level": "A",
"teams": 32,
"nets": 7
}
]
}
]
}
]
The problem is that I cannot just run a ceil filter on the Math.ceil(divisions.count/5) to get a value for divisions.nets or Math.ceil(_id.count/5) to get _id.nets because they are wrong in some cases.
I need to be able to total divisions.levels.nets and push that into divisions.nets and add divisions.nets and put that value into _id.nets so the calculations work properly.
Any ideas on how to do this?

Answer 1

Something like this. Add $project stage to calculate the nets for level followed by $sum & $push nets for rest of $groups
Registration.aggregate([
{
"$group": {
"_id": {
"day": "$day",
"group": "$group",
"division": "$division",
"level": "$level"
},
"count": { "$sum": 1 }
}
},
{ $project: { count:1, nets: { $ceil : { $divide: [ "$count" , 5 ] } } } },
{
"$group": {
"_id": {
"day": "$_id.day",
"group": "$_id.group",
"division": "$_id.division"
},
"count": { "$sum": "$count" },
"nets": { "$sum": "$nets" },
"levels": {
"$push": {
"level": "$_id.level",
"teams": "$count",
"nets" : "$nets"
}
}
}
},
{
"$group": {
"_id": {
"day": "$_id.day",
"group": "$_id.group"
},
"count": { "$sum": "$count" },
"nets": { "$sum": "$nets" },
"divisions": {
"$push": {
"division": "$_id.division",
"count": "$count",
"nets:": "$nets",
"levels": "$levels"
}
}
}
}
])