Re: st: RE: yscale in anovaplot

[David Airey <david.airey@vanderbilt.edu>]

.

Typical plots in the context of a split plot design are here:

http://www.ats.ucla.edu/stat/stata/examples/kirk/kirkstata12.htm

-Dave

On Apr 26, 2009, at 1:19 PM, David Airey wrote:

> .
>
>
> In the simplest within subject design, the paired ttest, it makes  
> sense to plot the data by subject, a line per subject. Or if you  
> measure subjects repeatedly over time, it also makes sense to keep  
> the graphic by subject. Or if you measure two groups, pre and post,  
> it makes sense to plot either two groups of different colored lines  
> (one line per subject) or ignore subject and make a profile plot as  
> other software does. As far as I can tell, none of the permutations  
> of the factors does this, and that is why I said anovaplot is for  
> between subjects designs only, or as the help says with maybe one  
> covariate. My query was as much to Diego, who seemed satisfied with  
> his use of -anovaplot- in a repeated measures context. I was just  
> curious what his final plot looked like and from what model.
> Cheers,
>
> -Dave
>
> On Apr 26, 2009, at 12:14 PM, Nick Cox wrote:
>
> > You use it the way you expect to be most fruitful.
> >
> > I'm not minded to go upstream and find out what the example is  
> > about, or
> > learn enough about the subject-matter to make a guess at what  
> > should be
> > most helpful.
> >
> > But the default -anovaplot- has no inbuilt intelligence. It's likely
> > that some permutation of the factors improves on the default plot,  
> > for
> > example
> >
> > anovaplot s a b
> >
> > A simple but important issue is that whenever identifiers are quite
> > arbitrary, putting them on one axis may not yield a clear picture. It
> > may be worth re-labelling identifiers to make structure clearer.
> >
> > Nick
> > n.j.cox@durham.ac.uk
> >
> > David Airey
> >
> > I always use it for between subjects ANOVAs. Perfect for that.
> >
> > The key thing in my response is that _I_ have not been satisfied with
> > my use in within subject designs or mixed models.
> >
> > Maybe I was not using it correctly. Let's use an example from UCLA
> > ATS, so that I can get it as correctly intended.
> >
> > From
> >
> > http://www.ats.ucla.edu/stat/stata/faq/xtmixed.htm
> >
> > just focusing on the ANOVA aspects of the page, let's do:
> >
> > use http://www.ats.ucla.edu/stat/stata/examples/kirk/spf2-4, clear
> > anova y a / s|a b a*b /, repeated(b)
> >
> > How do you use -anovaplot- here?
> >
> > -Dave
> >
> > On Apr 26, 2009, at 11:26 AM, Nick Cox wrote:
> >
> > > 2.1.1 is the latest publicly available version.
> > >
> > > -anovaplot- plots observed and fitted values after -anova- in  
> > > terms of
> > > predictor levels.
> > >
> > > It's a bit surprising to hear that you never found that useful. What
> > > do
> > > you do instead?
> > >
> > > A while back I went carefully through various classic texts on ANOVA
> > > from the 1950s. As I recall none of them included any plots based on
> > > data.
> > >
> > > Nick
> > > n.j.cox@durham.ac.uk
> > >
> > > David Airey
> > >
> > > I never found -anovaplot- useful for anything but between subject
> > > designs. I'd be curious to see the repeated measures plots using -
> > > anovaplot-.
> > >
> > > Is the version on SSC not the latest?
> > >
> > > I have
> > >
> > > . which anovaplot
> > > /Users/dairey/Library/Application Support/Stata/ado/plus/a/
> > > anovaplot.ado
> > > *! 2.1.1 NJC 6 November 2004
> > >
> > > -Dave
> > >
> > > On Apr 26, 2009, at 10:52 AM, Nick Cox wrote:
> > >
> > > > Thanks to Diego for this interesting question and to Thomas for
> > > > answering it so fully.
> > > >
> > > > To fill in a gap and to fill out the implicitly needed discussion:
> > > >
> > > > -anovaplot- is a program in the -modeldiag- package written up in  
> > > > the
> > > > Stata Journal within
> > > >
> > > > SJ-4-4  gr0009  . . . . . . . . . . Speaking Stata: Graphing model
> > > > diagnostics
> > > >     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N.
> > > > J. Cox
> > > >     (help anovaplot, indexplot, modeldiag, ofrtplot, ovfplot,
> > > >     qfrplot, racplot, rdplot, regplot, rhetplot, rvfplot2,
> > > >     rvlrplot, rvpplot2 if installed)
> > > >     Q4/04   SJ 4(4):449--475
> > > >     plotting diagnostic information calculated from residuals
> > > >     and fitted values from regression models with continuous
> > > >     responses
> > > >
> > > > There's also an equivalent package on SSC that includes older
> > > > versions
> > > > of these programs.
> > > >
> > > > The paper is accessible to all via
> > > >
> > > > http://www.stata-journal.com/sjpdf.html?articlenum=gr0009
> > > >
> > > > -anovaplot- is described on p.458. I add this comment, which is
> > > > relevant
> > > > to Diego's question:
> > > >
> > > > "It is curious that analysis-of-variance people typically draw
> > > > interaction plots but suppress the data, whereas regression people
> > > > prefer to draw scatterplots showing both observed and fitted  
> > > > values.
> > > > Admittedly, a complicated set of crossing lines showing  
> > > > interactions
> > > > may
> > > > seem to leave little scope for showing data effectively, while a
> > > > relatively
> > > > simple regression leaves plenty of scope, but the difference is
> > > > nevertheless intriguing."
> > > >
> > > > I still treasure a comment made by a senior Stata user, who might  
> > > > not
> > > > want to be named for this, to the effect that showing the data on  
> > > > the
> > > > graph typically confuses the issue.
> > > >
> > > > Nevertheless I'll think about adding a -nodata- option, possibly
> > > > with a
> > > > sting in the tail. (For example, it might -drop- all your data, or
> > > > some
> > > > such.)
> > > >
> > > > Nick
> > > > n.j.cox@durham.ac.uk
> > > >
> > > > Thomas Steichen
> > > > ===============
> > > >
> > > > Although you have suppressed printing a symbol for the data points
> > > > via
> > > > -scatter(msym(none))-, Stata still allows room for that invisible
> > > > data
> > > > in its y-axis range. Therefore you cannot reduce the range given  
> > > > the
> > > > way
> > > > the code is written. Editing the code to allow what you want is
> > > > pretty
> > > > straightforward.
> > > >
> > > > Change line:
> > > >             numlist "2/`= 1 + `: word count `fits'''"
> > > > To:
> > > >             numlist "1/`= 1 + `: word count `fits'''"
> > > >
> > > > And line:
> > > >         twoway scatter `y' `x1' if e(sample), `scatter' ///
> > > > To:
> > > >         twoway `scatter'  ///
> > > >
> > > > Then edit line:
> > > > program anovaplot, sort
> > > > To:
> > > > program anovaplot0, sort
> > > >
> > > > Save it with new name anovaplot0.ado and invoke it with command
> > > > -anovaplot0-
> > > >
> > > > Nick Cox's original will keep working and you'll have this one for
> > > > your
> > > > purpose.
> > > >
> > > > Of course, you could get fancy and add a -nodata- option that  
> > > > allows
> > > > both forms in a single program.
> > > >
> > > > Diego Bellavia
> > > > ==============
> > > >
> > > > I am trying to plot an ANOVA for repeated measures model using the
> > > > amazing anovaplot command.
> > > > Everything works fine except the yscale range. I need to reduce the
> > > > range and increase the scale
> > > > to make differences clear. So I tried:
> > > >
> > > > anovaplot level groups, scatter(msym(none)) yscale (range(-12 -24))
> > > > ylabel(-12 (2) -24)
> > > >
> > > > The problem is that I actually reduced the numbered range and the
> > > > labelling but now almost half of the graph
> > > > is empty. Is there any way to change the range so that I can take
> > > > advantage of all the graph extension ?
> > *
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