Impossible to calculate the area of a polygon using the formula $area

[alexCCI]

What is the bug or the crash?

It's impossible to calculate the area of a polygon using the formula $area, it returns a 'NaN' value. However, it remains functional when using geometric functions like area($geometry). The same applies to the perimeter.

Steps to reproduce the issue

1. Select a polygon layer.
2. Go to the fields calculator.
3. Try using the $area formula.

Versions

Tested in QGIS 3.36.2 and 3.34.6

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

No response

[pigreco]

OSGeo4W win 11 pro

I did a test with QGIS 3.34.6 AND 3.36.2, it works!

2024-05-08_08h27_10.mp4

[uclaros]

I did a test with QGIS 3.34.6 AND 3.36.2, it works!

Preview works as in your screencast, but the actual calculation of the field values returns nulls.

[pigreco]

it works for me

2024-05-08_11h09_14.mp4

[uclaros]

it works for me

Now I'm confused, it works for me too!
I could have sworn I replicated the issue!

[nyalldawson]

My gut feeling -- the crs is set incorrectly for the dataset, or it's using a crs which isn't valid for the actual area containing features.

[alexCCI]

The problem initially occurred in versions installed through OSGeo4W. A complete reinstallation of all components didn't help. I also tried installing the latest version from the standalone .msi file, but the problem persisted. I conducted tests with different layers, in different coordinate systems, and with various projects. Importantly, the area is calculated correctly using area($geometry).

[uclaros]

My gut feeling -- the crs is set incorrectly for the dataset, or it's using a crs which isn't valid for the actual area containing features.

This crossed my mind, but the preview displayed a value before clicking ok...

[nyalldawson]

Ok, let's close until a reproducible workflow is available

[uclaros]

@alexCCI can you share a project/data where you can replicate this?

[alexCCI]

In the end, you were right. The layer I was trying to work with had a personalized coordinate system without an EPSG code. I apologize for the inconvenience.