Carsten Dominik writes: > I have applied this patch, thank you for your contribution! My pleasure. > No hurry, better to get it complete and tested... > :-) I should have read this advice more carefully :-) Because before, when only sums where calculated as summaries, 0 was placed instead of empty or non numeric properties. This makes calcualtions wrong with min/mean/max operators. I only use complete tables so I did not notice this before now. So I have changed this behavior to ignore empty properties and also hanlde cases when all properties are wrong.