I had the need to add columns with the coordinates of polygons centroids. I came up with the following expressions to calculate X e Y, respectively:

[code] xmin(centroid($geometry)) ymin(centroid($geometry)) [/code]

The expression seems quite simple, but it toke me some time before I realize that, not having a x(geometry) and y(geometry) functions, I could use the xmin() and ymin() to get the coordinates of the polygons centroids. Since this wasn’t the first time I had to use this expressions, this post will work as a reminder for the future.