# Input Border Data from an External File in FreeFEM++
**URL:** https://community.freefem.org/t/input-border-data-from-an-external-file-in-freefem/3713
**Category:** General Discussion
**Created:** [January 27, 2025, 11:55am UTC](https://community.freefem.org/t/input-border-data-from-an-external-file-in-freefem/3713 "2025-01-27T11:55:56Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Amina1727](https://community.freefem.org/u/Amina1727)
#### Post date: [January 27, 2025, 11:55am UTC](https://community.freefem.org/t/input-border-data-from-an-external-file-in-freefem/3713/1 "2025-01-27T11:55:56Z")
Hello everyone,
I am currently working on a project in FreeFEM++ and would like to know how to read boundary coordinates from an external file. I have a file named Data.dat that contains
r and z values in a table format, for example:
r1 z1
r2 z2
r3 z3
My goal is to read this data and use it to define a boundary or contour in my computational domain. I’ve tried using an `ifstream` to read the file, but I encountered errors (e.g., “No operator .is for type ”).
Could anyone provide a working example or recommend an approach for:
1. Reading such an external file in FreeFEM++.
2. Using the data to define a boundary or mesh?
Thank you in advance for your help! Any suggestions or sample scripts would be greatly appreciated.
Best regards,
---
### Author:  [@fb77](https://community.freefem.org/u/fb77)
#### Post date: [January 30, 2025, 4:23pm UTC](https://community.freefem.org/t/input-border-data-from-an-external-file-in-freefem/3713/2 "2025-01-30T16:23:10Z")
You can do for example as
[borderdatatomesh.edp](https://community.freefem.org/uploads/short-url/tw2AUFfKFU7R6IQdHLksszTmn0r.edp) (2.6 KB)
I have taken as example input file `bdry.dat` as
```auto
6
0. 0.
1. 0.
2. 1.
1. 3.
0.5 5.
0. 1.
```
The first line contains the number of points on the boundary (6 in the example),
and next the x and y coordinates of the points.
They are supposed to represent the boundary oriented in the trigonometric sense.
I assume the data will represent a star-shaped domain, and I therefore add a point in the middle (coordinate 0.5, 0.5 in the file .edp) so that the mesh is made of triangles joining a boundary segment to the center.
After that you can refine the mesh (see file).
---
### Author:  [@fb77](https://community.freefem.org/u/fb77)
#### Post date: [January 31, 2025, 9:55am UTC](https://community.freefem.org/t/input-border-data-from-an-external-file-in-freefem/3713/3 "2025-01-31T09:55:34Z")
There is a much simpler way by using a multi-border
[borderdatatomesh.edp](https://community.freefem.org/uploads/short-url/1OdIGkDQ0hrwnZILTNozCpI25h.edp) (1.0 KB)
The domain needs not be star-shaped.
You have simply to set `nbsegborder` in order to define the level of discretization.
---
### Author:  [@Amina1727](https://community.freefem.org/u/Amina1727)
#### Post date: [February 11, 2025, 8:43pm UTC](https://community.freefem.org/t/input-border-data-from-an-external-file-in-freefem/3713/4 "2025-02-11T20:43:36Z")
Thank you, Professor , for your invaluable help and support. I truly appreciate your guidance.