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Hi there,

last time, this community forum was so helpful and I hope someone can help me this time around too…

I’m using the Clipper to clip polygons using the Group Processing feature. Only if the values of the attribute “att_1” are the same should the clipping occur. So far so good. However, it can be that att_1 is NULL (empty) and in this case, I would like to do Group Processing using attribute “att_2”. Is there a way to configure this in the Clipper directly?


With my humble knowlegde of FME, I would filter for att_1 being NULL and have two Clippers (one for Group Processing att_1 and one for Group Processing att_2) and then merge the two data streams again. But is there a more elegant way?

You can create a Attribut “_groupby” before to use it in the clipper.

I would indeed use Tom’s approach. Create an attribute, fill that with the values of att_1, unless att_1 is null, then use att_2. Can easily be done with a single AttributeCreator (use conditional value), and then you only need one Clipper, using the new attribute as GroupBy. If you don’t want to clutter your data, you can immediately remove the new attribute again, but it may come in handy later on as well, depending on what you need to do further on.

As an afterthought: I’d probably use a Tester right before the Clipper just to check that the new attribute actually has a value, just in case both att_1 and att_2 are null (I’ve been bitten by something similar on more than one occasion 😄).

Thanks for your input!

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