TI-Nspire CX II and TI-84 Plus CE: COUNTIF, SUMIF, AVERAGEIF
Introduction
Three popular spreadsheet functions are operating on elements of a list contingent of a criteria.
Let L be a list of numerical data.
COUNTIF(L, criteria): returns a count of all the elements that fit a criteria
SUMIF(L, criteria): returns the sum of all the elements that fit a criteria
AVERAGEIF(L, criteria): returns the arithmetic average of all the elements that fit a criteria
Example:
L = {0, 1, 2, 3, 4, 5, 6}
COUNTIF(L, "≥4") = 3.
Counts all the elements of L that are greater than or equal to 4.
SUMIF(L, "≥4") = 15
Sums all the element's of L that are greater than or equal to 4.
AVERAGEIF(L, "≥4") = 5
Returns the arithmetic average of L that are greater than or equal to 4.
Note that:
AVERAGEIF(L, criteria) = SUMIF(L, criteria) ÷ COUNTIF(L, criteria)
TI-Nspire CX II: The functions countif and sumif
The TI-Nspire has two built in functions countif and sumif. The averageif can easily be defined in the equation from the last section.
You can download a tns demonstration document here:
https://drive.google.com/file/d/1XfRyHSQz92TXGmzohhej0--wLYS0yxkF/view?usp=sharing
TI-84 Plus CE Programs: LISTIF
The program LISTIF calculates all three functions COUNTIF, SUMIF, and AVERAGEIF. There are two custom lists that are created as a result of this program:
List A: The input list.
List B: The list that meets the criteria.
To get the small "L" character, press [ 2nd ], [ stat ] (LIST), B* for the small L. The small L must be the first character of your list name. Once created, custom lists are shown under the LIST - NAMES menu.
Although I did not test this on previous calculators, this program should work on the TI-82, TI-83 family, and all of the TI-84 Plus family.
Program listing:
