How do you remove duplicate values in an array in Appian ?

Will use union() to remove the duplicate elements

Code:

Output:

Why union works here: union() merges lists, and the merged list holds each distinct value only once. That applies to duplicates inside a single list as well as across lists, so the output has no repeats even though both arguments are the same list.

The function expects at least two lists, so the list is passed twice. The second copy adds no new values, which leaves the first list with its duplicates removed.

Identify the duplicate elements in array and print it : Also they might may be a follow up question to write a code in Appain to print duplicate elements only from the given array. Below this code to print duplicate elements from the array

Code:

Output:

{"Naruto", "Itachi"}

Explanation:

This expression finds the names that appear more than once in a list and returns each of them once. Simply returns duplicates

What each part does

1. local!users is a list of six names. “Naruto” and “Itachi” each appear twice.
2. local!uniqueUsers: union(local!users, local!users) removes the duplicates, giving { "Naruto", "Sasuke", "Itachi", "Madhara" }, so each name is checked once instead of once per occurrence.
3. a!forEach(local!uniqueUsers, ...) loops over those four names, with fv!item holding the current one.
4. wherecontains(fv!item, local!users) returns the positions where the current name appears in the original list, duplicates included. For “Naruto” that is { 1, 4 }.
5. count(...) > 1 is true when the name appears at more than one position, so it is a duplicate.
6. if(..., fv!item, "") returns the name for a duplicate and an empty string otherwise.
7. reject(fn!isnull, ...) removes the empty strings, leaving only the duplicated names.

Step by step

After the loop, the list is { "Naruto", "", "Itachi", "" }. Reject(fn!isnull,..) removes the empty values form the array.

Result