R.QLNORM(x,logmean,logsd,lower_tail,log_p)
x: observation
logmean: mean of the underlying normal distribution
logsd: standard deviation of the underlying normal distribution
lower_tail: if true (the default), the lower tail of the distribution is considered
log_p: if true, log of the probability is used
This function returns the probability quantile function, i.e., the inverse of the cumulative distribution function, of the log-normal distribution.