public GetElement ( int rowIndex, int columnIndex ) : double | ||
rowIndex | int | The row number of the desired element |
columnIndex | int | The column number of the desired element |
Результат | double |
/// <summary> /// Inserts the passed Matrix into this Matrix starting at the specified index /// </summary> public Matrix InsertMatrixAt(Matrix passedMatrix, int destinationRow, int destinationColumn) { for (int row = 0; row < passedMatrix.NumberOfRows; row++) { for (int col = 0; col < passedMatrix.NumberOfColumns; col++) { this.SetElement(row + destinationRow, col + destinationColumn, passedMatrix.GetElement(row, col)); } } return this; }
// -------------------------------------------------------------------------------------------------------------- /// <summary> /// Performs Doolittle decomposition with partial pivoting and returns a combined LU matrix /// </summary> /// <param name="permutationArray">Keeps track of how the matrices have been rearranged during the calculation</param> /// <param name="toggle">is +1 or -1 (even or odd)</param> /// <returns></returns> public Matrix Decompose(out int[] permutationArray, out int toggle) { if (!this.IsSquare()) { throw new Exception("LU-Decomposition can only be found for a square matrix"); } Matrix decomposedMatrix = new Matrix(_matrix); // copy this matrix before messing with it permutationArray = new int[NumberOfRows]; // set up row permutation result for (int i = 0; i < NumberOfRows; ++i) { permutationArray[i] = i; } toggle = 1; // toggle tracks row swaps. +1 -> even, -1 -> odd //Loop through the columns for (int columnIndex = 0; columnIndex < NumberOfRows - 1; columnIndex++) { //Find largest value in the current column double maxOfColumn = Math.Abs(decomposedMatrix.GetElement(columnIndex, columnIndex)); int pivotRowIndex = columnIndex; // loop through all of the rows in this column for (int rowIndex = columnIndex + 1; rowIndex < NumberOfRows; rowIndex++) { if (Math.Abs(decomposedMatrix.GetElement(rowIndex, columnIndex)) > maxOfColumn) { maxOfColumn = Math.Abs(decomposedMatrix.GetElement(rowIndex, columnIndex)); pivotRowIndex = rowIndex; } } if (pivotRowIndex != columnIndex) // if largest value not on pivot, swap rows { double[] rowPtr = decomposedMatrix.GetRow(pivotRowIndex); decomposedMatrix.SetRow(pivotRowIndex, decomposedMatrix.GetRow(columnIndex)); decomposedMatrix.SetRow(columnIndex, rowPtr); int tmp = permutationArray[pivotRowIndex]; // and swap permutation info permutationArray[pivotRowIndex] = permutationArray[columnIndex]; permutationArray[columnIndex] = tmp; toggle = -toggle; // adjust the row-swap toggle } //Check to see if there is a zero on the diagonal. If so, try to get rid of it by swapping with a row that is beneath the row with a zero on the diagonal // double elementOnDiagonal = decomposedMatrix.GetElement(columnIndex, columnIndex); //if (Math.Round(elementOnDiagonal, 6) == 0.0) //{ // // find a good row to swap // int goodRow = -1; // for (int row = columnIndex + 1; row < decomposedMatrix.NumberOfRows; row++) // { // double element = decomposedMatrix.GetElement(row, columnIndex); // if (Math.Round(element, 6) != 0.0) // { // goodRow = row; // } // } // if (goodRow != -1) // { // // swap rows so 0.0 no longer on diagonal // double[] rowPtr = decomposedMatrix.GetRow(goodRow); // decomposedMatrix.SetRow(goodRow, decomposedMatrix.GetRow(columnIndex)); // decomposedMatrix.SetRow(columnIndex, rowPtr); // int tmp = permutationArray[goodRow]; // and swap perm info // permutationArray[goodRow] = permutationArray[columnIndex]; // permutationArray[columnIndex] = tmp; // toggle = -toggle; // adjust the row-swap toggle // } // else // { // // throw new Exception("Cannot use Doolittle's method on this matrix"); // } //} //Find the next value to insert into the decomposed matrix for (int rowIndex = columnIndex + 1; rowIndex < this.NumberOfRows; ++rowIndex) { double valueToStore = decomposedMatrix.GetElement(rowIndex, columnIndex)/decomposedMatrix.GetElement(columnIndex, columnIndex); decomposedMatrix.SetElement(rowIndex, columnIndex, valueToStore); for (int nextColumnIndex = columnIndex + 1; nextColumnIndex < NumberOfRows; ++nextColumnIndex) { double valueToStore2 = decomposedMatrix.GetElement(rowIndex, nextColumnIndex) - decomposedMatrix.GetElement(rowIndex, columnIndex)*decomposedMatrix.GetElement(columnIndex, nextColumnIndex); decomposedMatrix.SetElement(rowIndex, nextColumnIndex, valueToStore2); } } } // main column loop return decomposedMatrix; } // MatrixDecompose
public static Matrix ProjectiveMatrixToRotationMatrix(Matrix matrix) { var newMatrix = new Matrix(3, 3); for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { newMatrix.SetElement(i, j, matrix.GetElement(i, j)); } } return newMatrix; }