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QR Decomposition Calculator

Compute A = QR (Q orthogonal, R upper triangular)

Enter 2x2 Matrix

QR Decomposition Definition

A = Q × R
Q: Orthogonal matrix (QᵀQ = QQᵀ = I)
R: Upper triangular matrix
Columns of Q are orthonormal basis

QR decomposition factorizes a matrix into an orthogonal matrix Q and an upper triangular matrix R. It is widely used for solving linear systems and eigenvalue problems.

⚠ QR decomposition always exists for any matrix with linearly independent columns. It is numerically stable for solving linear systems.

What is QR Decomposition?

QR decomposition factorizes a matrix A into A = QR where Q is an orthogonal matrix (QᵀQ = I) and R is an upper triangular matrix. This decomposition is fundamental in numerical linear algebra.

Orthogonal Q

QᵀQ = I, columns are orthonormal basis vectors.

Upper Triangular R

R[i][j] = 0 for i > j, diagonal entries may be positive.

Numerical Stability

QR is numerically stable for solving linear systems.

Gram-Schmidt

Classical method using orthogonalization of columns.

Gram-Schmidt Process:
v₁ = a₁
e₁ = v₁ / ||v₁||
v₂ = a₂ - (a₂·e₁)e₁
e₂ = v₂ / ||v₂||
Q = [e₁ e₂ ... eₙ], R[i][j] = aⱼ·eᵢ

Applications

Least Squares Eigenvalues Linear Systems Matrix Inversion Numerical Analysis

Frequently Asked Questions

What is QR decomposition?▼
A = QR where Q is orthogonal (QᵀQ = I) and R is upper triangular. Useful for solving linear systems and eigenvalue problems.
How to compute QR?▼
Gram-Schmidt orthogonalization, Householder reflections, or Givens rotations.
Properties of QR?▼
Q is orthogonal (preserves norms), R is upper triangular. Unique if diagonal of R is positive.
Applications of QR?▼
Solving least squares, eigenvalue computation, matrix inversion, numerical stability.

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