NADA and cenmle
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