topic Re: How to get the index of a particular value/entry in a list? in Discussions

How to get the index of a particular value/entry in a list?

Neo — Fri, 09 Jun 2023 18:07:20 GMT

I have the following list, how do I get the index of SplPparameter?

myList = {paramter1, parameter2, parameter3, Splparameter, parameterN, parameterEnd};

Ans is 4 in the above example.

Re: How to get the index of a particular value/entry in a list?

txnelson — Tue, 14 Dec 2021 05:59:50 GMT

Here are a couple of ways to handle your question.

Names Default To Here( 1 );
// My solution when list items are expressions
myList = {paramter1, parameter2, parameter3, Splparameter, parameterN, parameterEnd};

For( i = 1, i <= N Items( mylist ), i++,
	If( myList[i] == Parse( "Splparameter" ),
		Break()
	)
);
Show( i );

// If elements are strings the contains can be used
myList = {"paramter1", "parameter2", "parameter3", "Splparameter", "parameterN", "parameterEnd"};
i = Contains( myList, "Splparameter" );

//  Same using Loc() function
i = loc(mylist,"Splparameter" );

Re: How to get the index of a particular value/entry in a list?

ian_jmp — Tue, 14 Dec 2021 17:24:16 GMT

In the case of expressions, you can also use 'Loc()' (which returns a column vector):

Names Default To Here( 1 );

myList = {paramter1, parameter2, parameter3, Splparameter, parameterN, parameterEnd, Splparameter};
Print(loc(mylist, Expr(Splparameter)));

Re: How to get the index of a particular value/entry in a list?

Mark_Bailey — Tue, 14 Dec 2021 14:02:23 GMT

If you know that the items are expressions, then this shorter code will work.

Names Default To Here( 1 );
// My solution when list items are expressions
myList = {paramter1, parameter2, parameter3, Splparameter, parameterN, parameterEnd};
Contains( myList, Expr( Splparameter ) );

If not, then you need a more general code like the one provided by @txnelson