R.PLNORM(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 cumulative distribution function of the log-normal distribution.