# Assemble matrix

**URL:** https://discourse.julialang.org/t/assemble-matrix/99469
**Category:** New to Julia
**Created:** [May 26, 2023, 10:06pm UTC](https://discourse.julialang.org/t/assemble-matrix/99469 "2023-05-26T22:06:14Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![mary](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mary/32/53139_2.png) [@mary](https://discourse.julialang.org/u/mary)
#### Post date: [May 26, 2023, 10:06pm UTC](https://discourse.julialang.org/t/assemble-matrix/99469/1 "2023-05-26T22:06:14Z")

</div>

i want to assemble a matrix from FE space and trial but it gives me errors. does anyone know about the solution?

```julia
uApp1(x) = VectorValue(0.0,0.0)
uApp2(x) = VectorValue(0.0,0.0)
uApp3(x) = VectorValue(0.0,-vAppMax)
U_Disp = TrialFESpace(V0_Disp ,[uApp1 ,uApp2 ,uApp3])
order = 1
reffe_Disp = ReferenceFE(lagrangian ,VectorValue{2,Float64},order)
V0_Disp = TestFESpace(model,reffe_Disp;conformity =:H1,
    dirichlet_tags = ["LeftSupport","RightSupport","LoadLine"],
    dirichlet_masks =[(false ,true), (true ,true), (false ,true)])
# uh = zero(V0_Disp)

assemble_matrix(fem_params.U_Disp, fem_params.V0_Disp)

```

i think it is a simple question for those who know julia well but not for me as a new user.  
thank you for your help

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<div class="post-metadata">

### Author: ![gdalle](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gdalle/32/27854_2.png) [@gdalle](https://discourse.julialang.org/u/gdalle)
#### Post date: [May 27, 2023, 6:43am UTC](https://discourse.julialang.org/t/assemble-matrix/99469/2 "2023-05-27T06:43:41Z")

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Hi Mary! Could you provide a complete reproducible example? I’m not sure what packages you’re using, or which error you’re getting, which makes it hard to debug

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<div class="post-metadata">

### Author: ![mary](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mary/32/53139_2.png) [@mary](https://discourse.julialang.org/u/mary)
#### Post date: [May 27, 2023, 5:30pm UTC](https://discourse.julialang.org/t/assemble-matrix/99469/3 "2023-05-27T17:30:23Z")

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Hi gdalle! Thank you for your response. sure i hope this works

```julia
using GridapGmsh
using Gridap
using Gridap.Geometry
using LinearAlgebra
using Gridap.Fields
using Gridap.TensorValues
const vAppMax = 0.1
order = 1
reffe_Disp = ReferenceFE(lagrangian ,VectorValue{2,Float64},order)
V0_Disp = TestFESpace(model,reffe_Disp;conformity =:H1,
    dirichlet_tags = ["LeftSupport","RightSupport","LoadLine"],
    dirichlet_masks =[(false ,true), (true ,true), (false ,true)])
uApp1(x) = VectorValue(0.0,0.0)
uApp2(x) = VectorValue(0.0,0.0)
uApp3(x) = VectorValue(0.0,-vAppMax)
U_Disp = TrialFESpace(V0_Disp ,[uApp1 ,uApp2 ,uApp3])
assemble_matrix(fem_params.U_Disp, fem_params.V0_Disp) do u, v
        (0.5 * (∫(C_mat⊙(∇(u) ⋅ ∇(v)))fem_params.dΩ))
    end

```