keeps only those cols that are in the joining rows
keep only elements in this matrix that also appear in the argument matrix
keeps only those rows that are in the joining column
like zipWithIndex.
like zipWithIndex.map but ONLY CHANGES THE VALUE not the index. Note you will only see non-zero elements on the matrix. This does not enumerate the zeros
Considering the matrix as a graph, propagate the column: Does the calculation: \sum_{j where M(i,j) == true) c_j
removes those cols that are in the joining column
removes any elements in this matrix that also appear in the argument matrix
removes those rows that are in the joining column
Write the matrix, optionally renaming row,col,val fields to the given fields then return this.