ublas/doc/samples/compressed_vector.cpp

#include <boost/numeric/ublas/vector_sparse.hpp>
#include <boost/numeric/ublas/io.hpp>

int main () {
    using namespace boost::numeric::ublas;
    compressed_vector<double> v (3, 3);
    for (unsigned i = 0; i < v.size (); ++ i)
        v (i) = i;
    std::cout << v << std::endl;
}