[R-sig-eco] Continuous (Non-Count) Skewed Data With Many Zeros

[Rich Shepard]

On Tue, 15 May 2012, Tom_Philippi at nps.gov wrote:

> Are those true zeros, or below detection limit values?

Tom,

   Recorded as a combination of both. Data were collected over ~31 years by
different folks, analyzed by different labs, and stored in spreadsheets
(gak!) with no standardized formatting. It's probably reasonable to assume
that any entry of zero is really below the detection limit; if the chemical
was actually not present it would still be below the detecion limit.

> My only experience with water chemistry data had non-detects, not zeros,
> and I had to use the NADA package. On the bright side, I didn't have to
> worry about lots of zeros...

   I'll go find the NADA package.

Thanks,

Rich

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