# Transpose of QR factorization

**URL:** <https://discourse.julialang.org/t/transpose-of-qr-factorization/101457>\
**Category:** General Usage\
**Tags:** linearalgebra\
**Created:** [July 10, 2023, 9:52pm UTC](https://discourse.julialang.org/t/transpose-of-qr-factorization/101457 "2023-07-10T21:52:27Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![shce](https://avatars.discourse-cdn.com/v4/letter/s/d78d45/32.png) [@shce](https://discourse.julialang.org/u/shce)\
**Post date:** [July 10, 2023, 9:52pm UTC](https://discourse.julialang.org/t/transpose-of-qr-factorization/101457/1 "2023-07-10T21:52:27Z")

</div>

Hello,

It seems that I am not able to call the transpose function to a QR factorization object. In version 1.9.1:

```julia
julia> using LinearAlgebra

julia> A = rand(3,3);

julia> F = qr(A);

julia> typeof(F)
LinearAlgebra.QRCompactWY{Float64, Matrix{Float64}, Matrix{Float64}}

julia> typeof(F) <: LinearAlgebra.QRCompactWY{<:Real}
true

julia> transpose(F)
ERROR: MethodError: no method matching transpose(::LinearAlgebra.QRCompactWY{Float64, Matrix{Float64}, Matrix{Float64}})

Closest candidates are:
  transpose(::Union{BitVector, BitMatrix})
   @ LinearAlgebra /Applications/Julia-1.9.app/Contents/Resources/julia/share/julia/stdlib/v1.9/LinearAlgebra/src/bitarray.jl:238
  transpose(::Number)
   @ Base number.jl:224
  transpose(::Tridiagonal{var"#s971", V} where {var"#s971"<:Number, V<:AbstractVector{var"#s971"}})
   @ LinearAlgebra /Applications/Julia-1.9.app/Contents/Resources/julia/share/julia/stdlib/v1.9/LinearAlgebra/src/tridiag.jl:621
  ...

Stacktrace:
 [1] top-level scope
   @ REPL[6]:1

```

However, it seems that a transpose function for such objects exists: [https://github.com/JuliaLang/julia/blob/02272f0cbda8d4c7f92583c4229659790c7c089f/stdlib/LinearAlgebra/src/qr.jl#L509](https://github.com/JuliaLang/julia/blob/02272f0cbda8d4c7f92583c4229659790c7c089f/stdlib/LinearAlgebra/src/qr.jl#L509)

What am I missing?

Thanks in advance.

shce

---

<div class="post-metadata">

**Author:** ![mbaz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mbaz/32/17295_2.png) [@mbaz](https://discourse.julialang.org/u/mbaz)\
**Post date:** [July 10, 2023, 10:52pm UTC](https://discourse.julialang.org/t/transpose-of-qr-factorization/101457/2 "2023-07-10T22:52:35Z")

</div>

It seems you’re looking at a different Julia branch. Make sure to browse the 1.9-release branch (or v1.9.1 tag):

> <https://github.com/JuliaLang/julia/blob/v1.9.1/stdlib/LinearAlgebra/src/qr.jl>

Note that you can still use `F'` to find the adjoint of `QR`.