Hi,
Consider a data.frame with concentrations (CONC) measured at various time
points (TIME) from each individual (ID). Assuming these concentrations are
log normally distributed, I would like them on my semi-log concentration
versus time plots.
I transformed concentrations first to ln(CONC) and then backtransformed
them.
dat$logconc<-logb(dat$CONC,base=exp(1))
error.bar(unique(dat$TIME),tapply(dat$CONC,dat$TIME,mean),
exp(tapply(dat$logconc,dat$TIME,stdev)),add=T )
But this did not provide the error bars I wanted; the upper and lower should
be equally distant from the mean, and they are not -> the lower is greater
than the upper.
Can anyone help?
thanks,
Kalas
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