Closed joethorley closed 9 years ago
Is bootstrapping a better option?
Hi Joe,
I think boostrapping could be a good option.
I think I would prefer boostrapping as it covers arbitrary serial correlation. But on the other hand, if we follow the HP paper, at least all the simulation testing has been done for us...
Good work
Just to chime in quickly here, I used the zyp package (http://cran.r-project.org/web/packages/zyp/index.html) for doing mann-kendall tests on groundwater levels (www.env.gov.bc.ca/soe/indicators/water/wells/index.html; methods and code are available on the page). It has a nice implementation of two forms of trend-free prewhitening to deal with serial autocorrelation.
great - that's really helpful - we're check it out!
The zyp package looks good! I don't know what your thoughts are on providing multiple methods for trend analysis, but it would seems sensible to implement the zyp method first as it is ready to go out the box. Then further methods could be added later.
great - we've got a plan!
closing as no longer need for trend analysis
Hi Joe,
I have stopped working on the trend test function. The zyp package still looks useful for assessing trends in the concentrations. But in trying it out on a TOTAL LEAD concentrations I ran into a few issues outlined below.
For consistency with previuos WQ analyses I think focusing on mean concetration between day 100 and day 200 between years using the ZYP package would be the way to go. At least this would also be the easiest thing to implement.
Sorry for commenting on a closed issue, but this seemed like the most appropriate place.
Thanks Colin,
That's great to get those notes and insights down.
Joe
is Mann-Kendall Trend Test with methods to accommodate for autocorrelation appropriate or should we use something else - definitely want something that makes minimal parametric assumptions and robust and also quick and ideally implemented in a bomber package... I think avoid Bayesian for sure