[R-sig-eco] General Question of Graphical Presentation

Gustaf Granath Gustaf.Granath at ebc.uu.se
Mon Feb 15 10:08:23 CET 2010


Hi,
This is usually an ignored issue in statistical textbooks - but very 
important when you put together a paper. You can find some suggestions 
in Gelman & Hill 2007. I like the idea of overlay-plots, where you plot 
your fitted model (with different scenarios) on top of your data.

Gustaf
> Hello, this is my first post although I have been a subscriber to the list
> for a couple years now, and this is more of a general question on data
> presentation than a specific R problem.  I am currently in a weekly group
> that has been working mainly through examples and data with lmer, and as of
> late we have been discussing the issue of how to present data.  We have been
> facing considerable debate on how to graphically display models that contain
> multiple factors and often significant interactions.
>
> Sometimes a final model contains several linear terms, factors and
> interactions. However when presenting the data as a figure it might be
> desirable only to plot the effect of one interaction between a linear
> variable and a factor, whilst controlling for the effect of other terms in
> the model (i.e. one should plot the model means, as given by other
> software). The question is how should one correctly do this?
>
> One approach would be to use the predict() function to obtain predicted
> values from the final model after setting the covariates to some nominal
> level. However, it is not clear how to correctly calculate the standard
> error for groups using this approach. Plus it is so far not possible to use
> predict() with lmer.
>
> Additionally, is it best to present the observed data in the figure with the
> model estimation?  And how should model variation be presented?
>
> Sorry, if this post is confusing, but it is a synthesis of questions from
> multiple people.
>
>
> Cheers,
>
> Mikey



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