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. |
<http://www.appl-ecosys.com> Voice: 503-667-4517 Fax: 503-667-8863
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