LASTINDEXOF

Finds the last instance of a substring in a text and returns its index.

Syntax:

LASTINDEXOF(text, substring)

text is what you are looking at.

substring is what you are searching for in text.

Example:

If A1 contains "Hello" and A2 contains "l":

LASTINDEXOF(A1, A2)

returns 3

Text:

Substring:

Result:

3

Application:

Analyzing Website User Data

Imagine you are a data analyst for an e-commerce website. You have a log of user actions, and you want to find the last time a specific user viewed a product page. This could be useful for a variety of reasons, such as:

Remarketing: You want to show a targeted ad for a product the user recently viewed.
Customer Support: A user calls with a question about a product, and you want to quickly see the last time they were looking at it.
Behavioral Analysis: You want to understand the typical path a user takes before making a purchase.

Let's say your data is stored in a simple array of strings, where each string represents a sequence of user actions for a single session.

User Action Log

The following table shows a log of actions for a user named "Alice". Each entry in the Session Actions column is a string representing the pages she visited, in order.

	Session ID	User	Session Actions
	A	B	C
1	101	Alice	homepage,category,productA,cart
2	102	Alice	homepage,search,productB,productA
3	103	Alice	homepage,category,productC,productA,productB,checkout
4	104	Alice	homepage,productA,productA

Using LASTINDEXOF

Your goal is to find the last time the string "productA" appears in each session's action log. The LASTINDEXOF function is perfect for this. It returns the index of the last occurrence of a specified substring within a string. If the substring is not found, it returns -1.

Let's apply LASTINDEXOF to the "Session Actions" for each session.

Session 101:
- "homepage,category,productA,cart"
- LASTINDEXOF("homepage,category,productA,cart", "productA") will return 19. This is the starting index of the only occurrence of "productA".
Session 102:
- "homepage,search,productB,productA"
- LASTINDEXOF("homepage,search,productB,productA", "productA") will return 24. This is the index of the last occurrence of "productA".
Session 103:
- "homepage,category,productC,productA,productB,checkout"
- LASTINDEXOF("homepage,category,productC,productA,productB,checkout", "productA") will return 27. This is the index of the last "productA" entry.
Session 104:
- "homepage,productA,productA"
- LASTINDEXOF("homepage,productA,productA", "productA") will return 18. This is the index of the second "productA", which is the last one in the string.

Result Table

Here is the updated table, showing the result of the LASTINDEXOF function for each session.

	Session ID	User	Session Actions	LASTINDEXOF("productA")
	A	B	C	D
1	101	Alice	homepage,category,productA,cart	18
2	102	Alice	homepage,search,productB,productA	25
3	103	Alice	homepage,category,productC,productA,productB,checkout	27
4	104	Alice	homepage,productA,productA	18