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RE: st: RE: yscale in anovaplot


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: yscale in anovaplot
Date   Sun, 26 Apr 2009 18:14:49 +0100

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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