The ΔList( Command
DELTALIST.GIF

Command Summary

Calculates the differences between consecutive terms of a list.

Command Syntax

ΔList(list)

Menu Location

Press:

  1. 2nd LIST to access the list menu.
  2. RIGHT to access the OPS submenu.
  3. 7 to select ΔList(, or use arrows.

Calculator Compatibility

TI-83/84/+/SE

Token Size

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

Related Commands

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