Manipulate Lists/Array

Question

Hi All, 
 Just wondering if anyone could help with a question on manipulating a list/array. 
 An example of what I am trying to do is select a row of building envelope elements or multiple rows based on a variable. 
 For example selecting every 3 rd row or even more complex selecting every 2 nd panel on every 4 th row. 
 As a basic example I thought I would start with a line with points and try and create a list that just showed every second point. 
 So starting with: {point1[0], point1[1], point1[2], point1[3], point1[4], point1[5], point1[6], point1[7]} 
 And returning: {point1[0], point1[2], point1[4], point1[6]} 
 I thought I could do it with a point by function node? 
 So I started testing but with no luck. My final function looked a bit like this:

function (Point[] Llist) 
 { 
 for (int i = 0; i < Llist.Count; i+=2) 
 { 
 Point pList = new Point(this). xxxxxxxxx ; 
 } 
 Point PPoint = new Point(pList); 
 }

But I am obviously missing something, I tried multiple options in place of the xxxxxxx but with no luck, maybe I am going down the wrong path! 
 Any tips would be welcome 
 
 Thanks 
 Wayne

Mueller · Answer

Hi Wayne, 
 For a one-dimensional list you could use the list method "MembersAt". If your list is food = {potato, egg, cucumber, broccoli, fish, steak}, then food.MembersAt({1,3,5}) is {potato, cucumber, fish}. 
 For multi-dimensional lists, you'd have to iterate through the nested lists; however, instead of recreating the items you want to select you could add them to a list of the type: 
 function (Point[][] pntarray, int dRow, int dItem)
{
 Point returnlist = {};
 for (int i = 0; i < pntarray.Count; i += dRow)
 {
 for (int j = 0; j < pntarray[i].Count; j += dItem)
 {
 returnlist.Add(pntarray[i][j]);
 }
 }
 return returnlist;
}
 
 This function code would reside in a FunctionCall node (or could be a named Script Function created in and added to the Functions dialog). 
 Additional refinements could be to add startRow and startItem and change the loops to start at those values, respectively, i.e. for (int i = startRow; &hellip; . 
 HTH, 
 Volker