Group by function don't work

I want to group these points by Y value.But it did’t work.What’s wrong.Thanks in advance.

What did not work exactly?

As you see, except list 0 , each list just have one point. So this funtion did’t work.

I don’t understand what you were expecting here…

In your case this node will group only points with equal Y coordinates. As you can see from your screenshot in list 0 all elements has equal Y coordinates. And in every other list the points are with different Y coordinate.

I have a list of points, and I flattened this points in order to group them by their Y value. Each list have the same Y value.But only the list 0 was ture, the others just had one point.

Some of the other lists have the same Y coordinate,but them had not been group in the same list.

From your screenshot everything looks ok. The node works as expected. I don’t know the Y coordinates of the rest of the points.