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bug #694: document that SparseQR::matrixR is not sorted.

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This commit is contained in:
Gael Guennebaud 2016-02-01 16:09:34 +01:00
parent ec469700dc
commit ff1157bcbf
1 changed files with 11 additions and 0 deletions
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11
Eigen/src/SparseQR/SparseQR.h
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@ -128,6 +128,17 @@ class SparseQR : public SparseSolverBase<SparseQR<_MatrixType,_OrderingType> >
inline Index cols() const { return m_pmat.cols();}
/** \returns a const reference to the \b sparse upper triangular matrix R of the QR factorization.
* \warning The entries of the returned matrix are not sorted. This means that using it in algorithms
* expecting sorted entries will fail. This include random coefficient accesses (SpaseMatrix::coeff()),
* and coefficient-wise operations. Matrix products and triangular solves are fine though.
*
* To sort the entries, you can assign it to a row-major matrix, and if a column-major matrix
* is required, you can copy it again:
* \code
* SparseMatrix<double> R = qr.matrixR(); // column-major, not sorted!
* SparseMatrix<double,RowMajor> Rr = qr.matrixR(); // row-major, sorted
* SparseMatrix<double> Rc = Rr; // column-major, sorted
* \endcode
*/
const QRMatrixType& matrixR() const { return m_R; }