Adding an option (weight_by_frequency) for allowing duplicate entities for dimension reduction and clustering.
If weight_by_frequency is true, dimension reduction and clustering are conducted with duplicate entities (clustering is weighted by each frequency).
If weight_by_frequency is false, dimension reduction and clustering are conducted with unique entities.
I also added different PCA options: incremental PCA and weighted PCA
Writing codes for issue #75.
Adding an option (weight_by_frequency) for allowing duplicate entities for dimension reduction and clustering.
If weight_by_frequency is true, dimension reduction and clustering are conducted with duplicate entities (clustering is weighted by each frequency). If weight_by_frequency is false, dimension reduction and clustering are conducted with unique entities.
I also added different PCA options: incremental PCA and weighted PCA