template<typename Derived>
class Eigen::SparseMapBase< Derived, WriteAccessors >
Common base class for writable Map and Ref instance of sparse matrix and vector.
class SparseMapBase
template<typename Derived>
- Returns
- a non-const reference to the value of the matrix at position i, j
If the element does not exist then it is inserted via the insert(Index,Index) function which itself turns the matrix into a non compressed form if that was not the case.
This is a O(log(nnz_j)) operation (binary search) plus the cost of insert(Index,Index) function if the element does not already exist.