[R] Nonparametric MANOVA [RESOLVED]

[Rich Shepard]

On Tue, 13 May 2014, Cade, Brian wrote:

> Your use of the term MANOVA suggests a multivariate response (Y).
> If what you really have is multiple factors (predictors), then this is a
> different modeling construct (multiple regression) and it would seem
> nonpartest() is not appropriate.

Brian,

   You are, of course, correct. I've not before had occasion to think of
MANOVA as a tool so I was ignorant until Don and you educated me. That's
much appreciated.

> I've been analyzing water quality constituents (one at a time as a
> univariate response) with multiple predictors (I'm using years, seasons
> within years, stream flow, location within watershed but anything you
> might include in a regression model could be included) in linear quantile
> regression (quantreg package). This is a semiparametric approach in the
> sense that I don't have to make any assumption about a particular
> distributional form of the error distribution since estimating the
> quantiles is estimating the inverse of an empirical cumulative
> distribution, but all the predictors have parameters associated with them.
> You can include contrasts for categorical predictors, interactions, etc.
> You also could relax the linear additive model by using smoothing
> functions (e.g., b-splines) on the predictors.

   Late yesterday I realized that what I really need is some form of
regression model. Your comments above are very helpful and I will now head
down this path.

Thanks very much,

Rich

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