The geomean functions returns the geometric mean. The geometric mean is calculated by multiplying all the values in a column and then taking the nth root of the product of n numbers. It is often used to find the average growth rates of a population or in finance the calculate in average interest rate over time.
There are two types of geometric mean functions.
Find the geometric mean for the world growth rate:
pop_geomean = GEOMEAN('world population growth'[growth rate])
Use when you want to find the geometric mean of an expression
Find the geometric mean for the inflation rate.
Geomean_x = GEOMEANX('inflation rate', 1 + 'inflation rate'[Inflation rate])
GEOMEANX is used to evaluate an expression over a table. In this case the expression is simply 1 + inflation rate. 1 is added onto the inflation rate, since the inflation rate is 0% in several years, which would incorrectly result in a geometric mean of zero.
The functions used above are plotted in Power BI to compare