Originally from Paul McMurdie, Ben Bolker, and Gregor on Stack Overflow: https://stackoverflow.com/questions/2602583/geometric-mean-is-there-a-built-in
gm_mean(x, na.rm = TRUE, zero.propagate = FALSE)
the geometric mean of the vector
vector of numeric values
logical TRUE/FALSE remove NA values
logical TRUE/FALSE. Allows the optional propagation of zeros.