topic Re: remove elements in a list in Discussions

remove elements in a list

gianpaolo — Wed, 07 Feb 2018 17:17:34 GMT

Hello,

someone can help me.....i have two lists like this:

MYLIST = {:empty, :empty2, :Name("A:k"), :Name("A:m"), :Name("A:x"), :Name("A:y"), :NA, :Name("D:3"), :Name("D:6"), :Name("D:8")};
DELCOLS= {:empty, :empty2};

i would like remove the elements of list DELCOLS from MYLIST

expected results:

 MYLIST = {:Name("A:k"), :Name("A:m"), :Name("A:x"), :Name("A:y"), :NA, :Name("D:3"), :Name("D:6"), :Name("D:8")}

thanks in advance

Gianpaolo

Re: remove elements in a list

txnelson — Wed, 07 Feb 2018 16:39:20 GMT

You would use the Remove() function. See the scripting index

Help==>Scripting Index

for details.

I strongly suggest you read the Scripting Guide. It contains a detail on how to manipulate lists

Help==>Books==>Scripting Guide

Re: remove elements in a list

Jeff_Perkinson — Wed, 07 Feb 2018 17:30:08 GMT

@txnelson is right, the Scripting Index and Scripting Guide are excellent resources.

To help you along the way though, check out the For() loop, Remove From(), As List() and Loc() functions.

MYLIST = {:empty, :empty2, :Name( "A:k" ), :Name( "A:m" ), :Name( "A:x" ), :Name( "A:y" ), :NA,
:Name( "D:3" ), :Name( "D:6" ), :Name( "D:8" )};
DELCOLS = {:empty, :empty2};

For( i = 1, i <= N Items( delcols ), i++,
	Remove From( mylist, As List( Loc( mylist, delcols[i] ) ) )
);

Re: remove elements in a list

ms — Wed, 07 Feb 2018 23:56:30 GMT

Jeff's code is great and use a clever way to remove any multiple instances of the unwanted items.

Just to illustrate that there's often more than one way to do things in JSL: here's an alternative approach using Associative Arrays.

(Note, all multiples would be removed)

MYLIST = {:empty, :empty2, :Name("A:k"), :Name("A:m"), :Name("A:x"), :Name("A:y"), :NA, :Name("D:3"), :Name("D:6"), :Name("D:8")};
DELCOLS = {:empty, :empty2};

// Remove DELCOLS from MYLIST. Retains original order of items. 
AA = Associative Array(MYLIST, 1 :: N Items(MYLIST));
MYLIST = (AA << Remove(Associative Array(DELCOLS)) << get keys)[Rank(AA << get values)];

// If order is not important, this simpler version works (items sorted alphabetically)
MYLIST_sorted = Associative Array(MYLIST) << Remove(Associative Array(DELCOLS)) << get keys;

Show(MYLIST, MYLIST_sorted);