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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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