It should be as simple as using the "sample" keyword in the boost::accumulators namespace, like:
using namespace boost::accumulators; accumulator_set< int, features<tag::weighted_sum> > acc( sample = 42 )
Thanks Eric. Indeed, it works ! But my problem was actually independent of this. I am using more features, and it seems that we can't use more than 4 tagged arguments !!! using namespace std; using namespace boost::accumulators; typedef accumulator_set<int, features<tag::weighted_mean, tag::weighted_density, tag::weighted_p_square_cumulative_distribution, tag::weighted_extended_p_square>, double> AccType1; typedef accumulator_set<int, features<tag::weighted_mean, tag::weighted_density, tag::weighted_p_square_cumulative_distribution>, double> AccType2; typedef accumulator_set<int, features<tag::weighted_mean, tag::weighted_density, tag::weighted_extended_p_square>, double> AccType3; double probs[] = {0.01,0.05, 0.25, 0.33, 0.5, 0.67, 0.75, 0.95, 0.99}; vector<double> q_probs(probs, probs + sizeof(probs) / sizeof(double)); AccType1 acc1(tag::weighted_density::cache_size = 10, tag::weighted_density::num_bins = 10, tag::weighted_extended_p_square::probabilities = q_probs, tag::weighted_p_square_cumulative_distribution::num_cells = 10); // compiles (4 tagged arguments) // AccType1 acc2(sample = 42, tag::weighted_density::cache_size = 10, // tag::weighted_density::num_bins = 10, // tag::weighted_extended_p_square::probabilities = q_probs, // tag::weighted_p_square_cumulative_distribution::num_cells = 10); // Error : does not compile (5 tagged arguments) AccType2 acc3(sample = 42, tag::weighted_density::cache_size = 10, tag::weighted_density::num_bins = 10, tag::weighted_p_square_cumulative_distribution::num_cells = 10); // compiles (4 tagged arguments) AccType3 acc4(sample = 42, tag::weighted_density::cache_size = 10, tag::weighted_density::num_bins = 10, tag::weighted_extended_p_square::probabilities = q_probs); // compiles (4 tagged arguments) I wanted acc2, so I thought my syntax using the "sample" keyword was wrong but it was not, as acc3 and acc4 do compile. Is that a bug ?