Question

I’d like to store multiple boost accumulataor_set in a stl map.

All the examples I read use accumulator_set as a local variable:

accumulator_set<int, stats<tag::rolling_mean> > acc(tag::rolling_window::window_size = 5);

acc(1);
acc(2);
acc(3);

cout << rolling_mean(acc);

However I want to store accumulator_set in a map. I tried to write code like this, but I got stuck:

map<int, accumulator_set<long, stats<tag::rolling_mean> > > avg;

void update(int id, long data){
    if(avg.count(id)==0){
        //key doesn't exist in map
        avg[id]= ;// How to create acc as in above example and store it in map?
    }
    accumulator_set<long, stats<tag::rolling_mean> > &acc = avg[id];
    acc(data);
}

void read(int id){
    cout << rolling_mean(avg[id]) ;
}

How do I create an accumulator_set as in above example and store it(reference or object) in map?

Answer 1

You can use insert():

typedef accumulator_set<long, stats<tag::rolling_mean> > acc_set_t;

if(avg.count(id)==0){
    //key doesn't exist in map
    avg.insert( std::make_pair(id, acc_set_t(/*init parameters here*/) ));
}