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From |
"Klink, Andrew" <KLINKA@email.chop.edu> |

To |
"statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |

Subject |
RE: Re: st: modify axis range in scatter graphs |

Date |
Tue, 23 Mar 2010 13:20:38 -0400 |

Thank you, Maarten. That is very helpful. There is one caveat: when I graphed the curve using the post-estimation variables as you suggest, it generates the same shape curve, but on a different scale on the y-axis. The initial -fpfitci- I ran generated a curve whose y-axis range is within 0-1 (or as a percent: 0-100, as it will be labeled). When I graph the curve from the generated variables as you describe, the y-axis range is from 0.5-3 (the curve should remain within 0-1). I can get around this by ylabel(.5(.5)3 .5"0" 1"20" 1.5"40" 2"60" 2.5"80" 3"100") to make it look exactly like the initial -fpfitci- graph. However, this may artificially shrink the real 95% CI. What should I look into to correct the y-axis issue? -- Andrew Klink, MPH Senior Clinical Research Assistant Children's Hospital of Philadelphia --- On Mon, 22/3/10, Klink, Andrew wrote: > I am having a similar issue trying to restrict my y-axis, which > cannot be circumvented by using "if yvar<=0", -yscale()-, or > -ylabel()- options. The problem is that I am including a fitted > line (-fpfitci- in this case) whose left end extends in negative > values for yvar. It does not make sense to show the curve where > y < 0; as such, I am trying to restrict the y-axis from 0 to > 100. Any suggestions? There is a subtle difference here. Graphs like -twoway fpfitci-, -twoway lfit-, etc. are wrappers that combine fitting a model and graphing the result. So what you see is the consequence of your (implicit) model. You can adjust the model if you think the model is inappropriate. I tried the -estcmd- and -estopts- and -predopts- options, but it seemed to me that by default -fpfitci- plots the linear predictor, and specifying -predopts(mu)- results in an error. *-------------------- begin example -------------------------- sysuse auto, clear // seems to plot the linear predictor rather than the // predicted weight twoway fpfitci weight mpg, estcmd(glm) estopts(link(log)) // produces the error message "option mu not allowed" twoway fpfitci weight mpg, estcmd(glm) estopts(link(log)) predopts(mu) *---------------------- end example -------------------------- However, since these are only convience commands, you can just as easy reproduce these graphs from first principle: *------------- begin example -------------------- sysuse auto, clear fracpoly : glm weight mpg, link(log) predict xb , xb predict se , stdp gen lb = exp(xb - invnormal(0.975)*se) gen ub = exp(xb + invnormal(0.975)*se) gen mu = exp(xb) twoway rarea lb ub mpg, sort astyle(ci) || /// line mu mpg, sort lpattern(solid) *------------- end example ---------------------- Hope this helps, Maarten -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * 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/

**Follow-Ups**:**RE: Re: st: modify axis range in scatter graphs***From:*Maarten buis <maartenbuis@yahoo.co.uk>

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