Extracting row/columns on a grid of points

Hi, just a simple thing I don’t quite understand.
I’ve created a grid of points on a surface and now want to get rid of the points along the surgace edge. I have managed to isolate the points I want to get rid of by extracting rows/columns, but if I do a ‘set diference’ on the original grid, the outcome is a set of points, but not a grid anymore.
(just to be clear I would like to keep the points in red and get rid of the green ones - and still have a grid)

thanks!
m.

Sigh…

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I’m sorry I have read through those before and I tried to follow them. It’s a simple question and I guess it is basic but I still havent found a way - no need to share de GH file as it’s clearly seen on the screenshot. I have been conscise about my wording&title, attached a descriptive picture.

So what am I doing wrong?

You did nothing wrong.
You’ll just have to solve the problem by your own.
Usually the best way to understand the problem is by seeing the problem directly.
With your question we have just a picture and some assumptions…

Sets are lists (or branches), so:

“Set Difference” works with lists; maybe you can do the thing you need with set difference, but it would be hard as you are working with a full tree.

matrix offset.gh (9.0 KB)

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Hey Riccardo,
thank you for your suggestions, I will have a try with both of them and see if it works.
And I will improve my questions in the future to make it easier for everyone. I just thought I was missing a very obvious component (like a substraction for grids or so).

I’m new to this, so thanks for the patience!

BW
mireia

Following this: https://www.grasshopper3d.com/forum/topics/datatree-selection-rules
You can also do this:

matrix offset_V2.gh (10.9 KB)

But it is somehow more complex and have lower control.

@DavidRutten it could be interesting to have the possibility to use "-1 " in paths, so this would have been solved with a: {!0 and !-1}[!0 and !-1]
Tried path mapper syntax here: {!0 and !(path_count-1)}[!0 and !(item_count-1)]
It doesn’t work:

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Okay,
So it works now, I have used both the set difference method & the split list. Set Difference is the component I was using initially but forgot to simplify my data trees.
Somehow in the difference one I have so substract the 0 column twice for it to work - but anyways.
Haven’t tried David’s method yet.

GH file here:TS explorations - grid panelling for review.gh (37.6 KB)

thanks again Riccardo!
m.