[R] < symbols in a data frame

Claudia Beleites claudia.beleites at ipht-jena.de
Wed Jul 9 22:49:58 CEST 2014

Hi Sam,

> But this may not be the important issue here at all. If "<k" means the
> value is left censored at k -- i.e. we know it's less than k but not
> how much less -- than Sarah's proposal is not what you want to do.
> Exactly what you do want to do depends on context, and as it concerns
> statistical methodology, is not something that should be discussed
> here. Consult a local statistician if this is a correct guess.
I'd like to chime in with Bert's advise here. Unless the < LOQs are
very few*, they have the potential to seriously mess up any further data

Actually, I'd recommend you go one step back and ask the analysis lab
whether they can supply you with the uncensored data, specifying the
LOQ separately. 

A while ago I posted some illustrations about such censoring
at LOQ situations on cross validated, which may help you in forming a
decision how to go on:

Claudia (Analytical Chemist & Chemometrician)

*or you know that they'll not matter for the particular data analysis
you want to do

Claudia Beleites, Chemist
Leibniz Institute of Photonic Technology 
Albert-Einstein-Str. 9
07745 Jena

email: claudia.beleites at ipht-jena.de
phone: +49 3641 206-133
fax:   +49 2641 206-399

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