Internal function to get the matrix product when missing data (NA) is found in matrix Y.
matmult.syncsa(X, Y)A matrix, typically the standardized community matrix (W).
A matrix.
The matrix product.
The function ignore missing data when found in matrix Y. Before multiplication of matrices the missing data in Y are replaced by 0 and multiplication is performed, and then, an adjustment is performed. This adjustment is done by divide each cell of the product matrix by the sum of proportions of nonzero at X with complete data in Y. In SYNCSA context this adjustment is done by divide each cell of the product matrix by the sum of species proportion with trait data in Y. Important, the matrix X must be standardized, in other words, row totals must be equal to 1.