Extracting every Nth Item from a List

I have MAIN LIST A, from which I am trying to generate SUB LISTS A1, A2, & A3 from. SUB LIST A1 needs to contain every third item from MAIN LIST A, starting from index #0. SUB LIST A2 needs to contain every third item from MAIN LIST A, starting from index#1. SUB LIST A3 needs to contain every third item from MAIN LIST A, starting from index#2.

I need a way to extract every Nth item from a list, in the same way that Cull Nth works, just inversely-so.

I am fairly new to grasshopper, and I can see in my mind there is a solution but I am not familiar enough with the components yet.

I've read this thread:

http://www.grasshopper3d.com/forum/topics/copy-every-nth-item-of-a-...

But I didn't quite understand how to apply it to my situation.

Any suggestions would be greatly appreciated.

Thanks

Replies to This Discussion

Permalink Reply by Zack on April 10, 2015 at 11:34am

So far, I have culled every Nth, produced a new list, then culled every Nth from that list, resulting in a final list containing only 1/3 of the items from the original list. This works, but it's messy and non-adaptable in my opinion.

Closer, I used Cull Pattern, but it still seems like it might not allow for as much dynamic control as setting Boolean patterns would have to remain a manual process for differences in overall # of sub-lists to be generated.

Permalink Reply by ng5 Alex on April 10, 2015 at 12:11pm

Hello Zack,

you can try the following

cheers

alex

Permalink Reply by Zack on April 10, 2015 at 12:19pm

Alex, thanks for the quick reply!

I'm pretty new to Grasshopper, and didn't even realize you could add the +1..+N definitions onto the List Item component. That is really useful, and a little more elegant than the solution I had come up with !

Thanks again

Permalink Reply by ng5 Alex on April 10, 2015 at 12:25pm

you re welcome!

you can use ZUI to zoom in and add inputs and outputs in many components. also there is an expression x-1 in the second series output. (right click on the output to access the menu).

best,

alex

Permalink Reply by Zack on April 10, 2015 at 12:32pm

Thanks!

I've just not realized all the components yet that have the Zui Parameter option yet. I almost wish each component with that option had a little flag or some sort of indicator.

Permalink Reply by ng5 Alex on April 10, 2015 at 12:35pm

zooming in, kind of works like an indicator.

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