Add shiftRowsUp/shiftRowsDown methods

main/ejml-ddense/src/org/ejml/dense/row/CommonOps_DDRM.java

@@ -2770,6 +2770,48 @@ public static DMatrixRMaj permuteRowInv( int[] pinv, DMatrixRMaj input, DMatrixR
         return output;
     }
 
+    /**
+     * Fills all rows in the specified range with zeros
+     *
+     * @param start Index of the first row (inclusivce) to be filled
+     * @param end Index of the last row (exclusive) to be filled
+     */
+    public static void zeroRows(DMatrixRMaj a, int start, int end) {
+        Arrays.fill(a.data, start * a.numCols, end * a.numCols, 0);
+    }
+
+    /**
+     * Shifts all elements up by the specified number of rows.
+     * Vacated rows are set to zero.
+     *
+     * @param a A matrix. Modified.
+     * @param c Number of rows to shift by.
+     */
+    public static void shiftRowsUp(DMatrixRMaj a, int c) {
+        if (c < a.numRows) {
+            System.arraycopy(a.data, c * a.numCols, a.data, 0, (a.numRows - c) * a.numCols);
+            zeroRows(a, a.numRows - c, a.numRows);
+        } else {
+            a.zero();
+        }
+    }
+
+    /**
+     * Shifts all elements down by the specified number of rows
+     * Vacated rows are set to zero.
+     *
+     * @param a A matrix. Modified.
+     * @param c Number of rows to shift by.
+     */
+    public static void shiftRowsDown(DMatrixRMaj a, int c) {
+        if (c < a.numRows) {
+            System.arraycopy(a.data, 0, a.data, c * a.numCols, (a.numRows - c) * a.numCols);
+            zeroRows(a, 0, c);
+        } else {
+            a.zero();
+        }
+    }
+
     /**
      * <p>Performs absolute value of a matrix:<br>
      * <br>

main/ejml-ddense/test/org/ejml/dense/row/TestCommonOps_DDRM.java

@@ -921,6 +921,50 @@ public void insert() {
         }
     }
 
+    @Test
+    public void shiftRowsUp() {
+        DMatrixRMaj A = RandomMatrices_DDRM.rectangle(5, 6, 0, 1, rand);
+
+        DMatrixRMaj B = new DMatrixRMaj(5, 6);
+
+        for (int n = 0; n <= A.numRows; n++) {
+            B.set(A);
+            CommonOps_DDRM.shiftRowsUp(B, n);
+            for (int row = 0; row < A.numRows - n; row++) {
+                for (int col = 0; col < A.numCols; col++) {
+                    assertEquals(A.get(row + n, col), B.get(row, col), UtilEjml.TEST_F64);
+                }
+            }
+            for (int row = A.numRows - n; row < A.numRows; row++) {
+                for (int col = 0; col < A.numCols; col++) {
+                    assertEquals(0.0, B.get(row, col), UtilEjml.TEST_F64);
+                }
+            }
+        }
+    }
+
+    @Test
+    public void shiftRowsDown() {
+        DMatrixRMaj A = RandomMatrices_DDRM.rectangle(5, 6, 0, 1, rand);
+
+        DMatrixRMaj B = new DMatrixRMaj(5, 6);
+
+        for (int n = 0; n <= A.numRows; n++) {
+            B.set(A);
+            CommonOps_DDRM.shiftRowsDown(B, n);
+            for (int row = 0; row < n; row++) {
+                for (int col = 0; col < A.numCols; col++) {
+                    assertEquals(0.0, B.get(row, col), UtilEjml.TEST_F64);
+                }
+            }
+            for (int row = n; row < A.numRows; row++) {
+                for (int col = 0; col < A.numCols; col++) {
+                    assertEquals(A.get(row - n, col), B.get(row, col), UtilEjml.TEST_F64);
+                }
+            }
+        }
+    }
+
     @Test
     public void addEquals() {
         DMatrixRMaj a = new DMatrixRMaj(2, 3, true, 0, 1, 2, 3, 4, 5);