# Is matrix multiplication not associative?

**URL:** <https://discourse.julialang.org/t/is-matrix-multiplication-not-associative/127231>\
**Category:** New to Julia\
**Tags:** question, error, matrix\
**Created:** [March 21, 2025, 4:09pm UTC](https://discourse.julialang.org/t/is-matrix-multiplication-not-associative/127231 "2025-03-21T16:09:38Z")\
**Posts on this page:** 1\
**Showing post:** 17

<div class="post-metadata">

**Author:** ![WalterMadelim](https://avatars.discourse-cdn.com/v4/letter/w/3e96dc/32.png) [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Post date:** [March 22, 2025, 11:18pm UTC](https://discourse.julialang.org/t/is-matrix-multiplication-not-associative/127231/17 "2025-03-22T23:18:17Z")

</div>

> [@stevengj](#):
>
> For most applications in linear algebra, I would say that adjoint is generally what you want

In the exact literal meaning, `transpose` is the essentially desired operation (since Complex number is _not_ involved in my context). At least they show up differently in Julia REPL

```julia
julia> transpose(x)
1×3 transpose(::Vector{Float64}) with eltype Float64:
 0.715859 0.0920015 0.183793

julia> x'
1×3 adjoint(::Vector{Float64}) with eltype Float64:
 0.715859 0.0920015 0.183793

```

> [@stevengj](#):
>
> an important operation in linear algebra is its relationship to inner products

Not only inner product, maybe equally important in _outer product_ as well.  
I may `transpose` other objects as well (e.g. `Array{JuMP.GenericVariableRef{Float64}, 1}` in [this](https://discourse.julialang.org/t/inner-product-grammar-is-neater-than-sum-index-in-jump-modeling-but-triggers-warning/124528/28) post)

---

_[View the full topic](https://discourse.julialang.org/t/is-matrix-multiplication-not-associative/127231)._