public double[] columnSums(){
            double[] sums = new double[this.numberOfColumns];
            for(int i=0; i<this.numberOfColumns; i++){
                sums[i] = 0.0;
                for(int j=0; j<this.numberOfRows; j++){
                    sums[i] += this.matrix[j][i];
                }
            }
            return sums;
        }