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Hi everyone,
I am working on a project where I need to conduct non-seasonal and
seasonal trend tests of multiply censored data (i.e., data with
multiple detection
limits).
An old thread on this mailing list
(http://r-sig-ecology.471788.n2.nabble.com/Seasonal-Mann-Kendall-with-multiple-detection-limits-td7578991.html
[1])
suggests that it is possible to perform these types of trend tests in
R using functions from USGS packages:
1. USGSwsQW package has a function called kendallATS.test
that performs a non-seasonal Mann-Kendall trend test;
2. restrend package has a function called censSeaken that
performs a seasonal Kendall trend test.
Now, I looked for the USGSwsQW package and couldn't find it.
Instead, I found the USGS package smwrQW
(https://rdrr.io/github/USGS-R/smwrQW/), [2] which
includes the function kendallATS.test. The restrend package I could
find and it does include the censSeaken function.
The syntax of the kendallATS.test function is kendallATS.test(x, y,
na.rm = TRUE), where in my case x will stand for year and y will be a
concentration
subjected to multiple detection limits. According to the help file,
y needs to be 'any data that can be converted to a left-censored data
object'.
The USGS packages seem to have an as.lcens() function which would
enable me to specify y as a left-censored vector of concentration
values subjected to
a single censoring limit. But they also have an as.mcens() function
which would accept multiple censoring/detection limits.
Initially, I thought that kendallATS.test would accept both lcens and
mcens data values. But it only accepts lcens data values, so I am not
sure
whether we are supposed to somehow convert mcens to lcens data values
prior to feeding them to kendallATS.test? If we are supposed to do
this
conversion, I am also not sure how the conversion should work as far
as as.lcens is concerned.
As an example, if y consists of the values "
Links:
------
[1]
http://r-sig-ecology.471788.n2.nabble.com/Seasonal-Mann-Kendall-with-multiple-detection-limits-td7578991.html
[2] https://rdrr.io/github/USGS-R/smwrQW/),
[3] mailto:isabe...@ghement.ca
[4] http://sitemail.wvthosting.com/<a href=
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