TI-BASIC:Deltalist
Command Summary
Calculates the differences between consecutive terms of a list.
Command Syntax
ΔList(list)
Menu Location
Press:
- 2nd LIST to access the list menu.
- RIGHT to access the OPS submenu.
- 7 to select ΔList(, or use arrows.
TI-83/84/+/SE
2 bytes
ΔList( calculates the differences between consecutive terms of a list, and returns them in a new list.
ΔList({0,1,4,9,16,25,36})
{1 3 5 7 9 11}
Advanced Uses
The ΔList( command is very nearly the inverse of the CumSum( command, which calculates the cumulative sums of a list. For any list, ΔList(cumSum(list)) will return the same list, but without its first element:
ΔList(cumSum({1,2,3,4,5,6,7}))
{2 3 4 5 6 7}
Removing the first element would otherwise be a difficult procedure involving the seq( command, so this is a useful trick to know.
If a list is sorted in ascending order, min(ΔList(list)) will return 0 (false) if there are repeating values in the list, and a value corresponding to true if they are all distinct.
Error Conditions
- ERR:INVALID DIM is thrown if ΔList( is run on a single element list.
