# How is function related to mesh?

**URL:** <https://fenicsproject.discourse.group/t/how-is-function-related-to-mesh/467>\
**Category:** Uncategorized\
**Created:** [March 29, 2019, 2:59am UTC](https://fenicsproject.discourse.group/t/how-is-function-related-to-mesh/467 "2019-03-29T02:59:29Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![mapengfei-nwpu](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/mapengfei-nwpu/32/117_2.png) [@mapengfei-nwpu](https://fenicsproject.discourse.group/u/mapengfei-nwpu)\
**Post date:** [March 29, 2019, 2:59am UTC](https://fenicsproject.discourse.group/t/how-is-function-related-to-mesh/467/1 "2019-03-29T02:59:29Z")

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Hello !

I am new to fenics and something puzzles me when i was trying this:

```auto
from fenics import *
import matplotlib.pyplot as plt
mesh = UnitSquareMesh(8,8)
V = FunctionSpace(mesh, "P", 1)
u = Function(V)
u.vector()[0] = 10
print(mesh.coordinates()[0])
plot(u)
plt.show()

```

In my opinion, after modifying the `u.vector()[0]` , the value of u at point `mesh.coordinates()[0]` should be changed. However, the picture painted shows that the value of u at point (0.0, 1.0) was changed.

How strange! Who can explain it?

---

<div class="post-metadata">

**Author:** ![Lukas\_O](https://avatars.discourse-cdn.com/v4/letter/l/b38774/32.png) [@Lukas\_O](https://fenicsproject.discourse.group/u/Lukas_O)\
**Post date:** [March 29, 2019, 7:54am UTC](https://fenicsproject.discourse.group/t/how-is-function-related-to-mesh/467/2 "2019-03-29T07:54:24Z")

</div>

Take a look at this Tutorial:

[https://fenicsproject.org/pub/tutorial/sphinx1/.\_ftut1006.html#degrees-of-freedom-and-function-evaluation](https://fenicsproject.org/pub/tutorial/sphinx1/._ftut1006.html#degrees-of-freedom-and-function-evaluation)

---

<div class="post-metadata">

**Author:** ![mapengfei-nwpu](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/mapengfei-nwpu/32/117_2.png) [@mapengfei-nwpu](https://fenicsproject.discourse.group/u/mapengfei-nwpu)\
**Post date:** [March 29, 2019, 3:11pm UTC](https://fenicsproject.discourse.group/t/how-is-function-related-to-mesh/467/4 "2019-03-29T15:11:35Z")

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Thank you very much !

Coordinates are reordered when constructing `FunctionSpace` V .

```auto
coordinates = V.tabulate_dof_coordinates()

```

instead of

```auto
coordinates = mesh.coordinates()

```

It might be right now !