Average MongoDB - mongodb

Question

The only thing I am trying to do is to get the average of Emision_C02 consumed at 10pm for all the days in location:1. The collection, db.datos_sensores2, has documents within like:
{
"_id" : ObjectId("609c2c2d420a73728827e87f"),
"timestamp" : ISODate("2020-07-01T02:15:00Z"),
"sensor_id" : 1,
"location_id" : 1,
"medidas" : [
{
"tipo_medida" : "Temperatura",
"valor" : 14.03,
"unidad" : "ºC"
},
{
"tipo_medida" : "Humedad_relativa",
"valor" : 84.32,
"unidad" : "%"
}
]
}
{
"_id" : ObjectId("609c2c2d420a73728827e880"),
"timestamp" : ISODate("2020-07-01T02:15:00Z"),
"sensor_id" : 2,
"location_id" : 1,
"medidas" : [
{
"tipo_medida" : "Emision_CO2",
"valor" : 1.67,
"unidad" : "gCO2/m2"
},
{
"tipo_medida" : "Consumo_electrico",
"valor" : 0.00155,
"unidad" : "kWh/m2"
}
]
}
I wrote this:
db.datos_sensores2.aggregate([
{$project:{timestamp:{$dateFromString:{dateString:'$timestamp'}},"_id":0, "me-didas":{$slice:["$medidas",-1]},"location_id":1}},
{$addFields:{Hora:{$hour:"$timestamp"}}},
{$match:{'Hora':{$in:[10]},'medidas.tipo_medida':"Emision_CO2", "location_id":1}},
{$group:{ _id: null, Avg_Emision_CO2:{$avg: "$medidas.valores"}}}])
But nothing happen....

Answer 1

pls refer to https://mongoplayground.net/p/-LqswomHWsY
I have noticed few things first of all hour comes to be 2 in above example and not 10. Second the variable/field names are not correct so i have updated it.
[{$unwind: {
path: '$medidas',
}}, {$addFields: {
Hora: {
$hour: "$timestamp"
}
} }, {$match: {
"Hora": {
$in: [2]
},
"medidas.tipo_medida": "Emision_CO2",
"location_id": 1
} }, {$group: {
_id: null,
Avg_Emision_CO2: {
$avg: "$medidas.valor"
}
}}]
Pipeline stages:
unwind: as $medidas is array we can unwind it so it will be easy to filter only "Emision_CO2",
addfield: add houre from timestamp
match: to match "medidas.tipo_medida": "Emision_CO2",
group: to get average