Get unique/distinct column values via rest - SharePoint Online

Hi All,
Im trying to use the code below to retrieve duplicate valuesof the Line field in my sharepoint list 

function getListItems(url, listname, query, complete, failure) {
    $.ajax({
        url: url + "/_api/web/lists/getbytitle('" + listname + "')/items" + query,
        method: "GET",
        headers: { "Accept": "application/json; odata=verbose" },
        success: function (data) {
            complete(data.d); 
        },
        error: function (data) {
            failure(data);
        }
    });
}


getListItems('https://site','Test','?$top=5',
   
 function(items){    
     //I can get the arrays here, how can i retrieve the item values
     console.log(items)
    
     var Names = groupBy(items,'Line');
      //This give me undefined error
       console.log(Names)

       
    },
    
    
    function(error){
       console.log(JSON.stringify(error));
    }
    
    
);

function groupBy(items,propertyName)
{
    var result = [];
    $.each(items, function(index, item) {
       if ($.inArray(item[propertyName], result)==-1) {
          result.push(item[propertyName]);
       }
    });
    return result;
}