Difference between revisions of "MAPREDUCE Elite"

There are 99 unique commodities and 15 categories.

Find the average price of each category, round to the nearest whole number.

db.commodities.mapReduce(
  function(){
    emit(1, 1);
  },
  function(k, v){
    return Array.sum(v);
  },
  {out: {inline: 1}}
);

db.commodities.mapReduce(function(){emit(this.category,this.average_price);},function(k,v){return Math.round(Array.sum(v)/v.length);},{out:{inline:1}});

Non-populated systems without stations do not have an allegiance, and should be ignored.

Show the amount of systems following each type of allegiance.

db.systems.mapReduce(
  function(){
    emit(1, 1);
  },
  function(k, v){
    return Array.sum(v);
  },
  {out: {inline: 1}}
);

db.systems.mapReduce(function(){if (this.allegiance!=null){emit(this.allegiance,1);}},function(k,v){return Array.sum(v);},{out:{inline:1}});

What are the populations of the three main factions?

db.systems.mapReduce(
  function(){
    emit(1, 1);
  },
  function(k, v){
    return Array.sum(v);
  },
  {out: {inline: 1}}
);

db.systems.mapReduce(function(){if(!isNaN(this.population)&&this.allegiance!=null&&this.allegiance!="Independent"&&this.allegiance!="Anarchy"){emit(this.allegiance,this.population);}},function(k,v){return Array.sum(v);},{out:{inline:1}});

How much Hydrogen Fuel is owned by each faction? Limit your query to the first 5000 stations.

db.systems.mapReduce(
  function(){
    emit(1, 1);
  },
  function(k, v){
    return Array.sum(v);
  },
  {out: {inline: 1}}
);

db.systems.mapReduce(function(){if(this.stations)for(let i=0;i<this.stations.length;i++){let t=this.stations[i];if(t.listings&&t.allegiance)for(let s=0;s<t.listings.length;s++){let n=t.listings[s];"Hydrogen Fuel"===n.commodity&&emit(t.allegiance,n.supply)}}},function(i,t){return Array.sum(t)},{out:{inline:1},limit:5e3});

These powers have allegiance to a faction, but the systems they control do not nescessarily have the same allegiance that they do.

    {   '_id': 'Zemina Torval',
        'value': {   'Alliance': 0.0,
                     'Anarchy': 0.0,
                     'Empire': 39.0,
                     'Federation': 3.0,
                     'Independent': 5.0}}]

Show the allegiance of each of the power's systems

db.systems.mapReduce(
  function(){
    emit(1, 1);
  },
  function(k,v){
    return Array.sum(v);
  },
  {
    query: {"power_control_faction": {"$exists": 1}},
    out: {inline: 1}
  }
);

db.systems.mapReduce(function(){emit(this.power_control_faction,{[this.allegiance]:1});},function(_,v){let a={"Alliance":0,"Anarchy":0,"Empire":0,"Federation":0,"Independent":0};for(let i=0;i<v.length;i++){let b=v[i];a.Alliance+=b.Alliance||0;a.Anarchy+=b.Anarchy||0;a.Empire+=b.Empire||0;a.Federation+=b.Federation||0;a.Independent+=b.Independent||0;}return a;},{out:{"inline":1},query:{"power_control_faction":{"$exists":1}},sort:{"_id":1}});

Using the result from the previous question, guess the power's allegiance by the faction that the majority of their systems follow.

To achieve this, you'll need to use the finalize: function(k, v){} in the third argument to find the key with the largest value.

{
    "_id" : "Zemina Torval",
    "value" : "Empire"
}

db.systems.mapReduce(
  function(){
    emit(1, 1);
  },
  function(k, v){
    return Array.sum(v);
  },
  {
    finally: function(k, v){
      return v;
    },
    query: {"power_control_faction": {"$exists": 1}},
    out: {inline: 1}
  }
);

db.systems.mapReduce(function(){emit(this.power_control_faction,{[this.allegiance]:1});},function(k,v){let a={"Alliance":0,"Anarchy":0,"Empire":0,"Federation":0,"Independent":0};for(let i=0;i<v.length;i++){let b=v[i];a.Alliance+=b.Alliance||0;a.Anarchy+=b.Anarchy||0;a.Empire+=b.Empire||0;a.Federation+=b.Federation||0;a.Independent+=b.Independent||0;}return a;},{finalize:function(k,v){return Object.keys(v).reduce((a,b)=>v[a]>v[b]?a:b);},out:{"inline":1},query:{"power_control_faction":{"$exists":1}},sort:{"_id":1}});