[R] NADA and cenmle

[Rich Shepard]

On Thu, 14 Mar 2013, Shane Carey wrote:

> Ah ok, thanks. I understand now. The data are chemical concentrations but
> are reported back as negative values. I have a Lower limit of detection
> (LLD) of 1 for one element but a value of -2.9 gets reported back to me.
>
> One last question, for a different element the LLD is reported as 10,
> anything <= 10 is given a value of -10. So, I now have:
> Data          Censored
> -10             TRUE
> -10             TRUE
> 20             FALSE
>
> In order for this to work in the NADA package, it must be transformed to:
>
> Data          Censored
> 10             TRUE
> 10             TRUE
> 20             FALSE

   Yep.

   Your first example would be recorded as

   1	TRUE

and your second example as

   10	TRUE

   Now, if both limits reflect different times or analytical methods for the
same chemical constituent, then you need two additional columns for the
lowest value (0) and the LLD (1 or 10) and a different analytical approach
for multiple reporting levels.

   Otherwise, you're on your way.

Rich

-- 
Richard B. Shepard, Ph.D.          |   Integrity - Credibility - Innovation
Applied Ecosystem Services, Inc.   |
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