public Matrix subtractColumnMeans(){
            Matrix mat = new Matrix(this.numberOfRows, this.numberOfColumns);

            for(int i=0; i<this.numberOfColumns; i++){
                double mean = 0.0;
                for(int j=0; j<this.numberOfRows; j++){
                    mean += this.matrix[j][i];
                }
                mean /= this.numberOfRows;
                for(int j=0; j<this.numberOfRows; j++){
                    mat.matrix[j][i] = this.matrix[j][i] - mean;
                }
            }
            return mat;
        }