I want to remove empty cells to obtain a map map like (b) from the above map (a). Do you know a simple way to do it?
If you want to delete the data - open attribute table and select by expression and delete - here is a screenshot of expression - your expression will be different e.g. fieldname is NULL or fieldname <=0
In layer Properties, define a
Provider Feature Filter like
"value" > 0 - all features where this condition is not met will not be shown on the map. See documentation.