[R] NADA package/cenboxplot() method: maximum censored percentage

[Rich Shepard]

On Thu, 16 Aug 2012, David L Lorenz wrote:

>  The cenboxplot function uses cenros to estimate the censored values. The
> cenros function requires at least 2 uncensored observations to be able to
> do the regression. The cenros function does issue a warning when there are
> more than 80% censored data, but that is suppressed in cenboxplot.

   There must be something other than > 2 uncensored observations in my data
that prevent cenboxplot from functioning. For example, dissolved arsenic
concentrations have 578 total observations. Of these, 180 (31.14%) are
censored and 398 are uncensored. Both number of uncensored observations and
the percentage of censored observations appear to be well within plotable
limits, but cenboxplot() returns this error:

cenboxplot(as.d$quant, as.d$ceneq1, as.d$era, range=1.5, main='Dissolved
Arsenic', ylab='Concentration (mg/L)', xlab='Time Period')
Error in if ((length(obs[censored])/length(obs)) > 0.8) { :
   missing value where TRUE/FALSE needed

   I would like to understand how the function obtains a censored ratio > 0.8
when it is actually 0.3114.

   Displaying the data frame, as.d, has a logical TRUE or FALSE for each row;
it can be provided if needed.

Rich