How to split a list based on the nr. of item in every branch?

Hi,

Can anyone tel me, how to split a list based on the nr. of item in each branch?

I would like to separate this list in 2 lists based on the nr. of items in each branch so one list contains only the branches with 3 items and one list with the branches with 2 items...

Thanks
//A

Replies to This Discussion

Permalink Reply by Andrew Heumann on December 7, 2010 at 8:54am

Feed the data into a "list length" component, test for equality (list length = 2) and then use "dispatch" to separate the data into two sets of branches. If having the resulting data contain branches with 0 items bothers you, you can use "clean tree" to remove those empty branches.

Permalink Reply by Ali Tabatabai on December 7, 2010 at 10:14am

Thanks, do you have any idea if it's possible to solve it in the Path Mapper?

Best
//A

Permalink Reply by Andrew Heumann on December 7, 2010 at 1:12pm

I don't think it is... unless there's some secret way to get the length of a list in a path mapper that I don't know about.

Permalink Reply by Ali Tabatabai on December 7, 2010 at 1:25pm

...well, we have the "item_count" in the Path Mapper but I'm not sure how to use it properly! I remember David mentioning a syntax for the Path Mapper, but I can't find that post...

Best
//A

Permalink Reply by Andrew Heumann on December 7, 2010 at 2:50pm

Ah, I had no idea!

Here's the trick:

use path mapper to map from whatever it is to start i.e. {0;0;A} to {(If(item_count=2,0,1))}

Because an equality expression evaluates to true or false which convert automatically to zero or one, you can even simplify it to map to {item_count=2} and leave it at that. But by nesting the if solution as above, it would be possible to separate lists of 3 or more different lengths.

Permalink Reply by Ali Tabatabai on December 7, 2010 at 3:09pm

ahh... didn't know about the "if"!

Thanks
//A

Permalink Reply by taz on December 7, 2010 at 4:05pm

Wait, "If" statements work with pathmapper now?

I know they just became available in expressions...

Permalink Reply by Andrew Heumann on December 7, 2010 at 4:38pm

they do indeed! I think everything that's valid in an expression is valid in a path mapper.

Permalink Reply by taz on December 7, 2010 at 8:07pm

Good to know... Now I just need to remember.

Permalink Reply by Kris Hammerberg on December 7, 2010 at 8:41pm

Wouldn't it be more flexible to use the list length and dispatch? Path mapper always seem so rigid to me. Most changes in the up stream definition will invalidate your expressions.

Still, I'd like to see some documentation on available path mapper and expression syntax. Did you find that post by David?

Permalink Reply by Andrew Heumann on December 7, 2010 at 9:07pm

the post in question (I believe) is here: http://www.grasshopper3d.com/forum/topics/subdivide-down-paths-with...

but believe it or not, the documentation is right in grasshopper; just double click the path mapper icon in the toolbar and a help doc comes up with a detailed explanation including the special placeholders item_count, path_count, and path_index. (in a little tiny note at the bottom)

quote:

There are additional placeholders available for target masks which allow you to track your overall progress in the data tree iteration.
The "path_index" placeholder is an integer which is incremented for every new data tree branch that gets loaded. For example the "{path_index}" target mask would simplify all branches in the entire tree, while keeping all branches separate.
The "path_count" placeholder represents the total number of branches in the current tree.
The "item_count" placeholder represents the total number of items in the current branch.

Permalink Reply by Kris Hammerberg on December 7, 2010 at 9:24pm

Thanks! I always forget to look there. A bad habit I got when those help tabs were not as helpful as they are today.