The RANK.EQ function in Google Sheets is used to determine the rank of a specified value within a dataset.

It returns the rank of a value as a numeric value. Here's how the function works:

value: This is the value for which you want to determine the rank within the dataset.

data: This is the range or array of values that contains the dataset.

is_ascending (optional): This parameter indicates whether the values in the dataset are sorted in ascending or descending order. If set to TRUE or omitted, the values are assumed to be in ascending order.

If set to FALSE, the values are assumed to be in descending order.

The RANK.EQ function assigns a rank to the specified value by comparing it with all the values in the dataset.

If there are ties (values that are the same), the function assigns the same rank to all the tied values, and the next rank is skipped.

Here's an example to illustrate the usage of RANK.EQ:

=RANK.EQ(A2, A1:A5, TRUE)

In this example, A2 is the value for which you want to determine the rank, and A1:A5 is the range containing the dataset. The third parameter, TRUE, indicates that the values are sorted in ascending order.

The function will return the rank of the value in cell A2 within the range A1:A5.

Note that the RANK.EQ function is one of the several rank-related functions available in Google Sheets. There is also RANK, which handles ties differently, and RANK.AVG, which assigns the average rank to tied values.