# Contour Label and Area Calculation - U magnitude in ParaView

**URL:** https://discourse.paraview.org/t/contour-label-and-area-calculation-u-magnitude-in-paraview/8884
**Category:** ParaView Support
**Created:** [February 2, 2022, 8:06pm UTC](https://discourse.paraview.org/t/contour-label-and-area-calculation-u-magnitude-in-paraview/8884 "2022-02-02T20:06:07Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![limpideyes](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/l/f475e1/32.png) [@limpideyes](https://discourse.paraview.org/u/limpideyes)
#### Post date: [February 2, 2022, 8:06pm UTC](https://discourse.paraview.org/t/contour-label-and-area-calculation-u-magnitude-in-paraview/8884/1 "2022-02-02T20:06:07Z")

</div>

Hello,

I have got questions about labelling contours and calculating the area of a certain wind speed.

Question 1:  
How can I label wind speed (U magnitude) at each contour?  
e.g. 10.00, 9.98, 9.96, etc.

Question 2:  
How can I calculate the area (m²) of a certain U magnitude in a dashed area?  
e.g. If the dashed area is 500m², and if this dark orange colour represents 9.96 (U magnitude), I’d like to know how much area (m²) 9.96 U magnitude occurs in a dashed area (500m²).

Please see the attached image.

 ![Question - Contour Cal](https://discourse.paraview.org/uploads/default/original/2X/d/d43ea19a620deb66e3e6218ee9a10948f1f87ccb.jpeg)

Please help,

Thanks in advance!

---

<div class="post-metadata">

### Author: ![pavel](https://discourse.paraview.org/user_avatar/discourse.paraview.org/pavel/32/8287_2.png) [@pavel](https://discourse.paraview.org/u/pavel)
#### Post date: [February 3, 2022, 8:22am UTC](https://discourse.paraview.org/t/contour-label-and-area-calculation-u-magnitude-in-paraview/8884/2 "2022-02-03T08:22:56Z")

</div>

Hello Mary,

Regarding question #1:  
[Is it possible to add labels to contour lines?](https://discourse.paraview.org/t/is-it-possible-to-add-labels-to-contour-lines/1466)  
Example made based on that discussion (using _Interactive Select Points On_ tool + _Edit-\>Find Data_):

![Countour_labeling](https://discourse.paraview.org/uploads/default/original/2X/3/3e606806b596ef5df34c49fcf8d959f56a470887.png)

Regarding question #2:  
you could apply Countour filter with requested range of U magnitude values, then CellSize filter, and finally IntegrateVariables filter. In the Information panel you’ll see the area of interest. Example:

1.Model

 ![1_Model](https://discourse.paraview.org/uploads/default/original/2X/6/6f8ae00230a9d6bc839ebbc63610f1fc5ef9df6c.png)

2.Countour filter:

2A. Set range:

![2a_Countour_filter_range](https://discourse.paraview.org/uploads/default/original/2X/7/7b11bf17b5fa005fb63ab8f2c49c2945589d7bbd.png)

2B. View after filter applying:

 ![2b_Countour_filter_range_result](https://discourse.paraview.org/uploads/default/original/2X/2/280d8b1a0b21826c676c14d91057271ac84633da.png)

3.CellSize filter - Area array (on Infromation tab):

![3_CellSize_Area_array](https://discourse.paraview.org/uploads/default/original/2X/2/239860e7b9df93d48630ec721c3e544483b0766a.png)

4.IntegrateVafiables filter - Total area of region of interest (on Information tab):

![4_IntegrateVariables_Area_for_U_magnitute_selected_range](https://discourse.paraview.org/uploads/default/original/2X/1/1c2e8b18abdcb8aeb2cb6abdf913fb341e72f221.png)

You can also use Python Calculator filter for the last step.

Hope it helps.

Best Regards,  
Pavel

---

<div class="post-metadata">

### Author: ![limpideyes](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/l/f475e1/32.png) [@limpideyes](https://discourse.paraview.org/u/limpideyes)
#### Post date: [February 3, 2022, 7:46pm UTC](https://discourse.paraview.org/t/contour-label-and-area-calculation-u-magnitude-in-paraview/8884/3 "2022-02-03T19:46:14Z")

</div>

Hi Pavel,

Thank you so much for your notes. It helps a lot!!

When tried, I have got some questions:

**Question 3**  
Selecting the zone that I am interested in:

 ![How to select area interested](https://discourse.paraview.org/uploads/default/original/2X/7/790c00c9768dc0c83dfe5f2c3c5fb8f25d68a999.jpeg)

I used ‘Select Cells With Polygon’ to select the zone. However, it is not handy. I have to select the zone that is 1.3 multiplied by a building width. In order to do that, I manually counted the cell number.  
Is there anyway that I can select the zone easily?

**Question 4**  
Contour for U is missing:

 ![extracted](https://discourse.paraview.org/uploads/default/original/2X/0/0a12ace1014c0e7822ebc2a9f9e6e83c071c4986.jpeg)

I extracted the zone from Edit/ Find Data/ Extract Selection.

 ![No Contour for U](https://discourse.paraview.org/uploads/default/original/2X/e/ef15d10ab0c833c6d4ae07b1c21a85bfb510e493.jpeg)

From the Extract Selection, I applied ‘contour filter’. Then, scrolled down for ‘contour By’. But there is no U magnitude. Only epsilon, k, nut, and p were shown. So, I could not get contour for U magnitude. How to get ‘contour By - U magnitude’?

Please help,

Thank you in advance!!