# Graphics with FF++

**URL:** <https://community.freefem.org/t/graphics-with-ff/1061>\
**Category:** General Discussion\
**Created:** [June 27, 2021, 11:12am UTC](https://community.freefem.org/t/graphics-with-ff/1061 "2021-06-27T11:12:14Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Aicha](https://avatars.discourse-cdn.com/v4/letter/a/ec9cab/32.png) [@Aicha](https://community.freefem.org/u/Aicha)\
**Post date:** [June 27, 2021, 11:12am UTC](https://community.freefem.org/t/graphics-with-ff/1061/1 "2021-06-27T11:12:14Z")

</div>

Hi!  
please what instructions we have to use to plot U(x,y,t) for t fixed?  
We have

```auto
mesh Th = square(N,N,[L*x,H*y]);
fespace Vh(Th,P1);
Vh U;

```

I try to use

```auto
ofstream foutU("U.txt");
for (real t=0;t<T;t+=dt) {
foutU << t << " " << U << endl;
}

```

This instruction gives a graphe in function of t but for which values of (x,y)? Please.

Regards

---

<div class="post-metadata">

**Author:** ![Aicha](https://avatars.discourse-cdn.com/v4/letter/a/ec9cab/32.png) [@Aicha](https://community.freefem.org/u/Aicha)\
**Post date:** [June 29, 2021, 7:21pm UTC](https://community.freefem.org/t/graphics-with-ff/1061/2 "2021-06-29T19:21:58Z")

</div>

Hi!

```auto
mesh Th = square(N,N,[L*x,H*y]);
fespace Vh(Th,P1);
Vh U;

```

for t fixed, what is the FF++ instructions to obtain the graphic in 2 D with Gnuplot or Paraview, of U(x,y,t) for all (x,y)?  
Please  
I found this instruction

```auto
int[int] Order = [1];string DataName = "u";savevtk("u.vtu", Th, u, dataname=DataName, order=Order);

```

but in this example there is no t, so we how we obtain the graphic en 2D of U(t,x,y) for t fixed?

Regards