How to get conditional average data for graph in mongodb? - node.js

Question

Data 1:
{
"_id" : "5eb922b4c019811689c8f8e3",
"createdAt" : "2020-05-10T19:30:00.000Z",
"isManual" : false,
"value" : 0.66
}
Data 2:
{
"_id" : "5eb922b4c019811689c8f8e3",
"createdAt" : "2020-05-10T19:30:00.000Z",
"isManual" : false,
"value" : 0.52
}
Data 3:
{
"_id" : "5eb922b4c019811689c8f8e3",
"createdAt" : "2020-05-10T19:30:00.000Z",
"isManual" : true,
"value" : 0.34
}
Now I need to generate a query for getting an average of value field. Consider isManual
key for average:
Response key expected:
total_fields = 3
manual_avg = 0.34 ((0.66 + 0.52)/3)
not_manual_avg = 0.13 ((0.34)/3)

Answer 1

You can try below aggregation query :
db.collection.aggregate([
/** group all docs in collection */
{
$group: {
_id: null,
total_fields: { $sum: 1 }, /** count total no.of docs */
manual_avg: { $avg: { $cond: [ "$isManual", 0, "$value" ] } }, /** If 'isManual' is true pass-in 0 else actual value to average */
not_manual_avg: { $avg: { $cond: [ "$isManual", "$value", 0 ] } }
}
},
/** Optional stage */
{
$project: { _id: 0,total_fields: 1, manual_avg: { $trunc: [ "$manual_avg", 2 ] }, not_manual_avg: { $trunc: [ "$not_manual_avg", 2 ] }
}
}
])
Test : mongoplayground

Answer 2

You can use $group along with $sum to count for total_field and to do the sum based on isManual condition using $cond
[
{
$group: {
_id: null,
count: {
$sum: 1
},
manual: {
$sum: {
$cond: [
"$isManual",
"$value", // add $value when $isManual is true
0
]
}
},
not_manual: {
$sum: {
$cond: [
"$isManual",
0,
"$value" // add $value when $isManual is false
]
}
}
}
},
{
$project: {
_id: false,
total_fields: "$count",
manual_avg: {
$divide: [
"$manual",
"$count"
]
},
not_manual_avg: {
$divide: [
"$not_manual",
"$count"
]
}
}
}
]