Hi,
There seems to be a bug in the GroupBy node.
If you have a datatable, and choose to Group on a column which is already unique (i.e. so the output has the same number of rows as the input), and in the aggregation section you choose to aggregate by "Geometric Mean" you would expect the numbers to remain unchanged.
However, this does not appear to be the case. For instance 15,300.0 becomes 15300.000000000004. Why should this be the case?
Simon.
Hi Simon,
I think this thread concerns the same topic:
http://tech.knime.org/forum/knime-general/incorrect-means-using-groupby-or-pivot-nodes
Unfortunately, calculating means (or any other number) in a computer is not as trivial as it seems and small imprecisions like this will always occur. In your case, no computation has to be performed at all but I assume that there is no special handling for this case available.
Hope this helps,
Nils
Thanks for the pointer, as you say it sounds like the same topic in this thread.
as a non programmer, it does sound strange to me why this is non trivial when my 20 year old pocket calculator can do it with ease.
but that's just my non programming ignorance!
simon.
Well, your pocket calculator doesn't show as much digits as the computer ;-)