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qrfact!

..  qrfact!(A [,pivot=Val{false}])

``qrfact!`` is the same as :func:`qrfact` when ``A`` is a subtype of ``StridedMatrix``, but saves space by overwriting the input ``A``, instead of creating a copy.

Examples

1. QR factorization of a matrix:

   julia> A = [1 2 3; 4 5 6; 7 8 9];
   julia> qrfact!(A)
   LinearAlgebra.QRCompactWY{Float64,Array{Float64,2}}
   QR factorization of a 3x3 matrix
   
   Q factor:
   3×3 LinearAlgebra.QRCompactWYQ{Float64,Array{Float64,2}}:
   -0.123091  -0.492366  -0.861640
   -0.492366  -0.771517   0.401620
   -0.861640   0.401620   0.309399
   
   R factor:
   3×3 Array{Float64,2}:
   -8.12404  -9.60114  -11.0782
    0.0       0.771517   1.54303
    0.0       0.0       -0.123091

   This example performs QR factorization of the matrix A in-place using qrfact!.

2. QR factorization with column pivoting:

   julia> A = [1 2 3; 4 5 6; 7 8 9];
   julia> qrfact!(A, Val{true})
   LinearAlgebra.QRPivoted{Float64,Array{Float64,2}}
   QR factorization with column pivoting of a 3x3 matrix
   
   Q factor:
   3×3 LinearAlgebra.QRPackedQ{Float64,Array{Float64,2}}:
   -0.123091  -0.492366  -0.861640
   -0.492366  -0.771517   0.401620
   -0.861640   0.401620   0.309399
   
   R factor:
   3×3 Array{Float64,2}:
   -8.12404  -9.60114  -11.0782
    0.0       0.771517   1.54303
    0.0       0.0       -0.123091
   
   P factor:
   3-element Array{Int64,1}:
   3
   2
   1

   This example performs QR factorization with column pivoting of the matrix A in-place using qrfact!.

Common mistake example:

julia> A = [1 2 3; 4 5 6; 7 8 9];
julia> qrfact!(A, Val{false}, 5)
ERROR: TypeError: Val{false} has no field ()

In this example, an invalid argument Val{false}, 5 is provided to qrfact!. It's important to provide the pivot argument as Val{false} or Val{true} without any additional parameters.

See Also

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