+ * new Matrix(new double[][] {{2, 3, 4}, {5, 6, 7})
+ * constructs
+ * (2 3 4)
+ * (5 6 7)
+ *
+ *
+ * Note that ragged arrays (with not all rows, or columns, of the same
+ * length), are not supported by this class. They can be constructed, but
+ * results of operations on them are undefined and may throw exceptions.
+ *
+ * @param values
+ * the matrix values in row-major order
*/
- public Matrix(double[][] value, int rows, int cols)
+ public Matrix(double[][] values)
{
- this.rows = rows;
- this.cols = cols;
- this.value = value;
+ this.rows = values.length;
+ this.cols = this.rows == 0 ? 0 : values[0].length;
+ this.value = values;
}
/**
- * DOCUMENT ME!
+ * Returns a new matrix which is the transposes of this one
*
* @return DOCUMENT ME!
*/
@@ -90,7 +98,7 @@ public class Matrix
}
}
- return new Matrix(out, cols, rows);
+ return new Matrix(out);
}
/**
@@ -113,15 +121,24 @@ public class Matrix
}
/**
- * DOCUMENT ME!
+ * Returns a new matrix which is the result of premultiplying this matrix by
+ * the supplied argument. If this of size AxB (A rows and B columns), and the
+ * argument is CxA (C rows and A columns), the result is of size CxB.
*
* @param in
- * DOCUMENT ME!
*
- * @return DOCUMENT ME!
+ * @return
+ * @throws IllegalArgumentException
+ * if the number of columns in the pre-multiplier is not equal to
+ * the number of rows in the multiplicand (this)
*/
public Matrix preMultiply(Matrix in)
{
+ if (in.cols != this.rows)
+ {
+ throw new IllegalArgumentException("Can't pre-multiply " + this.rows
+ + " rows by " + in.cols + " columns");
+ }
double[][] tmp = new double[in.rows][this.cols];
for (int i = 0; i < in.rows; i++)
@@ -137,16 +154,14 @@ public class Matrix
}
}
- return new Matrix(tmp, in.rows, this.cols);
+ return new Matrix(tmp);
}
/**
- * DOCUMENT ME!
*
* @param in
- * DOCUMENT ME!
*
- * @return DOCUMENT ME!
+ * @return
*/
public double[] vectorPostMultiply(double[] in)
{
@@ -166,37 +181,34 @@ public class Matrix
}
/**
- * DOCUMENT ME!
+ * Returns a new matrix which is the result of postmultiplying this matrix by
+ * the supplied argument. If this of size AxB (A rows and B columns), and the
+ * argument is BxC (B rows and C columns), the result is of size AxC.
+ * + * This method simply returns the result of in.preMultiply(this) * * @param in - * DOCUMENT ME! * - * @return DOCUMENT ME! + * @return + * @throws IllegalArgumentException + * if the number of rows in the post-multiplier is not equal to the + * number of columns in the multiplicand (this) + * @see #preMultiply(Matrix) */ public Matrix postMultiply(Matrix in) { - double[][] out = new double[this.rows][in.cols]; - - for (int i = 0; i < this.rows; i++) + if (in.rows != this.cols) { - for (int j = 0; j < in.cols; j++) - { - out[i][j] = 0.0; - - for (int k = 0; k < rows; k++) - { - out[i][j] = out[i][j] + (value[i][k] * in.value[k][j]); - } - } + throw new IllegalArgumentException("Can't post-multiply " + this.cols + + " columns by " + in.rows + " rows"); } - - return new Matrix(out, this.cols, in.rows); + return in.preMultiply(this); } /** - * DOCUMENT ME! + * Answers a new matrix with a copy of the values in this one * - * @return DOCUMENT ME! + * @return */ public Matrix copy() { @@ -204,13 +216,10 @@ public class Matrix for (int i = 0; i < rows; i++) { - for (int j = 0; j < cols; j++) - { - newmat[i][j] = value[i][j]; - } + System.arraycopy(value[i], 0, newmat[i], 0, value[i].length); } - return new Matrix(newmat, rows, cols); + return new Matrix(newmat); } /** @@ -738,20 +747,19 @@ public class Matrix } /** - * DOCUMENT ME! + * Returns an array containing the values in the specified column * - * @param n - * DOCUMENT ME! + * @param col * - * @return DOCUMENT ME! + * @return */ - public double[] getColumn(int n) + public double[] getColumn(int col) { double[] out = new double[rows]; for (int i = 0; i < rows; i++) { - out[i] = value[i][n]; + out[i] = value[i][col]; } return out; @@ -784,85 +792,4 @@ public class Matrix Format.print(ps, "%15.4e", e[j]); } } - - /** - * DOCUMENT ME! - * - * @param args - * DOCUMENT ME! - */ - public static void main(String[] args) throws Exception - { - int n = Integer.parseInt(args[0]); - double[][] in = new double[n][n]; - - for (int i = 0; i < n; i++) - { - for (int j = 0; j < n; j++) - { - in[i][j] = (double) Math.random(); - } - } - - Matrix origmat = new Matrix(in, n, n); - - // System.out.println(" --- Original matrix ---- "); - // / origmat.print(System.out); - // System.out.println(); - // System.out.println(" --- transpose matrix ---- "); - Matrix trans = origmat.transpose(); - - // trans.print(System.out); - // System.out.println(); - // System.out.println(" --- OrigT * Orig ---- "); - Matrix symm = trans.postMultiply(origmat); - - // symm.print(System.out); - // System.out.println(); - // Copy the symmetric matrix for later - // Matrix origsymm = symm.copy(); - - // This produces the tridiagonal transformation matrix - // long tstart = System.currentTimeMillis(); - symm.tred(); - - // long tend = System.currentTimeMillis(); - - // System.out.println("Time take for tred = " + (tend-tstart) + "ms"); - // System.out.println(" ---Tridiag transform matrix ---"); - // symm.print(System.out); - // System.out.println(); - // System.out.println(" --- D vector ---"); - // symm.printD(System.out); - // System.out.println(); - // System.out.println(" --- E vector ---"); - // symm.printE(System.out); - // System.out.println(); - // Now produce the diagonalization matrix - // tstart = System.currentTimeMillis(); - symm.tqli(); - // tend = System.currentTimeMillis(); - - // System.out.println("Time take for tqli = " + (tend-tstart) + " ms"); - // System.out.println(" --- New diagonalization matrix ---"); - // symm.print(System.out); - // System.out.println(); - // System.out.println(" --- D vector ---"); - // symm.printD(System.out); - // System.out.println(); - // System.out.println(" --- E vector ---"); - // symm.printE(System.out); - // System.out.println(); - // System.out.println(" --- First eigenvector --- "); - // double[] eigenv = symm.getColumn(0); - // for (int i=0; i < eigenv.length;i++) { - // Format.print(System.out,"%15.4f",eigenv[i]); - // } - // System.out.println(); - // double[] neigenv = origsymm.vectorPostMultiply(eigenv); - // for (int i=0; i < neigenv.length;i++) { - // Format.print(System.out,"%15.4f",neigenv[i]/symm.d[0]); - // } - // System.out.println(); - } }