On Mon, 22 Jan 2024, Martin Maechler wrote:
I think it is a good question, not really only about geo-chemistry, but about statistics in applied sciences (and engineering for that matter).
John W Tukey (and several other of the grands of the time) had the log transform among the "First aid transformations": If the data for a continuous variable must all be positive it is also typically the case that the distribution is considerably skewed to the right. In such a case behave as a good human who sees another human in health distress: apply First Aid -- do the things you learned to do quickly without too much thought, because things must happen fast ---to hopefully save the other's life.
Martin, Thanks very much. I will look further into this because toxic metals and organic compounds in geochemical collections almost always have censored lab results (below method dection limits) that range from about 15% to 80% or more, and there almost always are very high extreme values. I'll learn to understand what benefits log transforms have over compositional data analyses. Best regards, Rich ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
