Error in if (n > 0)

On Wed, 22 Aug 2012, David Winsemius wrote:

It is not saying there are zero values for concentration.... it is  
saying there are groups with zero elements:

 Thank you very much, David.

table(cu.t$ceneq1, cu.t$era)

     Mining Pre-mining
FALSE    723          0
TRUE     183          9

 That's interesting. I did not realize that cenboxplot() (or cenros)  
cannot
accommodate only censored data in one era.

I'm not sure I understand why you think there should be any estimate  
when all of one group is censored?

Sigh. I'll work around it.

In this case it appears that the plotting function is what threw the  
error:
 > cenboxplot(cu.t$quant, cu.t$ceneq1, cu.t$era, range=1.5, main='Total
+ Recoverable Copper', ylab='Concentration (mg/L)', xlab='Time Period')
Error in if (n > 0) (1L:n - a)/(n + 1 - 2 * a) else numeric() :
   argument is of length zero
 > traceback()
7: ppoints(obs)
6: hc.ppoints(obs, censored)
5: cenros(obs[group == i], cen[group == i])
4: cenros(obs[group == i], cen[group == i])
3: withCallingHandlers(expr, warning = function(w)  
invokeRestart("muffleWarning"))
2: suppressWarnings(cenros(obs[group == i], cen[group == i])$modeled)
1: cenboxplot(cu.t$quant, cu.t$ceneq1, cu.t$era, range = 1.5, main =  
"Total\nRecoverable Copper",
        ylab = "Concentration (mg/L)", xlab = "Time Period")

This succeeds in creating a plot

with( cu.t[cu.t$era=="Mining", ], cenboxplot(cu.t$quant, cu.t$ceneq1,  
range=1.5, main="Total Recoverable Copper", ylab="Concentration (mg/ 
L)", xlab="Time Period") )

David Winsemius, MD
Alameda, CA, USA