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From | "Martin Weiss" <martin.weiss1@gmx.de> |
To | <statalist@hsphsun2.harvard.edu> |
Subject | st: RE: How do I graph prediction of mean growth trajectory? |
Date | Fri, 21 May 2010 23:32:53 +0200 |
<> " A related question is this: If I have to produce these lines separately, creating six graphs, is there a way I can overlay them? " Overlaying these days is accomplished via -twoway- calls: *********** sysuse auto, clear tw (line price number) (line weight number) *********** This could be telescoped to -tw (line price weight number)- HTH Martin -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of David Torres Sent: Freitag, 21. Mai 2010 23:27 To: statalist@hsphsun2.harvard.edu Subject: st: How do I graph prediction of mean growth trajectory? Hello all, I am trying to graph expected growth in IQ scores by maternal IQ class and treatment/control group assignment. Since there are three maternal IQ classes and two group assignments, I should have six lines or growth curves. Now, my models were calculated using Stata's -xtmixed- command, so I've been following Rabe-Hesketh and Skrondal's text on multilevel modeling, 2nd edition, page 210-220. They give an example of how to graph growth, but the example does not include interactions nor does it allow for the slopes to change between some other time-varying covariate, which I have in my model. The outcome is test score, of course. The list of the predictor variables in the full model from which I would like to create my graphs follow: 1. age 2. age^2 3. assessment given (two different assessments over several years, so this is entered as a time-varying covariate. It would be great if I could get the slope to vary by assessment) - Stanford-Binet or Wechsler 4. home environment - 0/1, less stimulating/more stimulating 5. treatment - 0/1, control/treatment 6 & 7. maternal IQ class - 1/2/3, IQ<=75/IQ between 76&90/IQ between 91&110 1 is the reference category 8 & 9. interaction between treatment and maternal IQ class All of the variables in this model are significant, so I want to make sure that my graph accurately reflects that. Also, I understand that since interactions can be difficult to interpret sometimes a visual represention of the data are always good as an accompaniment. A related question is this: If I have to produce these lines separately, creating six graphs, is there a way I can overlay them? -------------------------------------------- David Diego Torres, MA(Sociology) PhD Candidate in Sociology * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/