I need to find out what expression has been used in the field calculator to populate a number of columns in the the attribute table in QGIS. Does anyone know how to get it to display this info? Like in excel when you select a cell with a formula it will display the formula in the box at the top of the page.
If the column is a virtual field it's easy :
- just open the layer properties, go to the "Source Field" tab and look for the "Comment" column. The expression is here and you can edit it (or simply view it better) by clicking the Ɛ.
If it's not a virtual field, I don't know of any way to recover the expression as only the resulting values are stored in the field. If you have access to the specific QGIS installation used to calculate the field you may try to have a look at the Expression String Builder in the "Recent" function category that saves the last few used expression and see if you could find one that seems to have be used.