I think I learned this morning the hard way of making test cases,
something I do often, but not always.......
public static void main(String args[])
{
double[][] data = {{1, 2, 3, 4},
{1.5, 2.5, 3.5, 4.5},
{2, 4, 6, 8},
{4, 5, 6, 7}};
Matrix m = new Matrix(data);
int[] rows = {0, 3};
int[] columns = {1, 2};
System.out.println(m.toSquareString());
System.out.println("Rows 0 to 2; columns 1 to 3");
System.out.println(m.getSubMatrix(0,2,1,3).toSquareString());
System.out.println("Rows 0 & 3; columns 1 & 2");
System.out.println(m.getSubMatrix(rows,columns).toSquareString());
System.out.println("Rows 0 to 2; columns 1 & 2");
System.out.println(m.getSubMatrix(0, 2 ,columns).toSquareString());
System.out.println("Rows 0 & 3; columns 1 to 3");
System.out.println(m.getSubMatrix(rows,1, 3).toSquareString());
System.out.println();
}
And that showed that this is the correct method:
/**
* Get a submatrix. Rows and columns are indicated
* counting from 0 to n-1.
*
* @param startRow Initial row index
* @param endRow Final row index
* @param startColumn Initial column index
* @param endColumn Final column index
* @return The subMatrix containing the data of the
* specified rows and columns
* @exception MatrixIndexException matrix dimension
* mismatch
*/
public Matrix getSubMatrix(int startRow, int endRow, int startColumn,
int endColumn) throws MatrixIndexException
{
Matrix subMatrix = new Matrix(endRow - startRow+1,
endColumn - startColumn+1);
double[][] subMatrixData = subMatrix.getDataRef();
try
{
for (int i = startRow; i <= endRow; i++)
{
for (int j = startColumn; j <= endColumn; j++)
{
subMatrixData[i - startRow][j - startColumn] = data[i][j];
}
}
}
catch (ArrayIndexOutOfBoundsException e)
{
throw new MatrixIndexException("matrix dimension mismatch");
}
return subMatrix;
}
O, I do have and do use two additional subMatrix versions as you can see....
Cheers,
kim
--
http://www.kimvdlinde.com
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