Wolfram: List. Delete Element
Delete by Index or Index Range
These are useful when the expression is considered as a flat list.
Delete N Items from Beginning or End
Drop[ expr, n]
-
- Delete n items from beginning.
- If n is negative, delete from end.
Drop[ {1, 2, 3, 4, 5}, 2 ] (* {3, 4, 5} *) Drop[ {1, 2, 3, 4, 5}, -2 ] (* {1, 2, 3} *)
Delete Nth Item
Drop[ expr, {n}]
-
delete nth item.
Drop[ {1, 2, 3, 4, 5}, {3} ] (* {1, 2, 4, 5} *)
Delete by Index Range
Drop[ expr, {m, n}]
-
delete mth to nth.
Drop[ {1, 2, 3, 4, 5}, {2,4} ] (* {1, 5} *)
Delete Parts by Position Spec
These are useful when the expression is considered as a nested list. You want to delete some nested part of the expression.
Delete[expr, pos]
-
delete the part at Position pos
Delete[ {a, {{b, c}, d}, e}, {1} ] (* {{{b, c}, d}, e} *) Delete[ {a, {{b, c}, d}, e}, {2} ] (* {a, e} *) Delete[ {a, {{b, c}, d}, e}, {3} ] (* {a, {{b, c}, d}} *) (* HHHH------------------------------ *) Delete[ {a, {{b, c}, d}, e}, {-1} ] (* {a, {{b, c}, d}} *)
Delete[expr, {pos1, pos2, pos3, etc}]
-
Delete a list of parts by Position
Delete[ {a, {{b, c}, d}, e}, {{1}} ] (* {{{b, c}, d}, e} *) Delete[ {a, {{b, c}, d}, e}, {{2}} ] (* {a, e} *) Delete[ {a, {{b, c}, d}, e}, {{1}, {2}} ] (* {e} *) Delete[ {a, {{b, c}, d}, e}, {{2, 1}} ] (* {a, {d}, e} *) Delete[ {a, {{b, c}, d}, e}, {{2, 1, 1}} ] (* {a, {{c}, d}, e} *)
Delete[expr, n]
-
shortcut for
Delete[expr, {n}]
the
{n}
means the Position, which is same as index nsame as delete element at nth index.
Delete[ {a, {{b, c}, d}, e}, 1 ] (* {{{b, c}, d}, e} *) (* same as *) Delete[ {a, {{b, c}, d}, e}, {1} ] (* {{{b, c}, d}, e} *) (* same as *) Delete[ {a, {{b, c}, d}, e}, {{1}} ] (* {{{b, c}, d}, e} *)
Delete by a Filtering Function
Select
Delete by a Filtering Pattern
Cases
DeleteCases
Delete Duplicates
DeleteDuplicates[expr]
-
Delete duplicates
DeleteDuplicates[ {3, x, 3, x, 4 } ] (* {3, x, 4} *)
Wolfram. List Operations
- Wolfram: List Operations
- Wolfram: List. Create (Table)
- Wolfram: Create Flat List (Range)
- Wolfram: List. Get Parts
- Wolfram: List. Add Element
- Wolfram: List. Delete Element
- Wolfram: List. Change Element
- Wolfram: List. Check Exist
- Wolfram: List. Filter
- Wolfram: List. Sort Reverse Order
- Wolfram: List. Reshape (split, group, flatten, transpose)
- Wolfram: List. Count, Group, Similar Items
- Wolfram: List. Combinatorics
- Wolfram: List. Join, Union, Intersection, Difference