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From |
Marquis Hawkins <marquishawkins82@hotmail.com> |

To |
STATA LISTSERV <statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: Convert SAS code to STATA |

Date |
Sat, 22 Sep 2012 15:59:25 -0400 |

My goal was to get change per year. with SAS using the contrast "-0.333 0.333 0 0 0 0 ", this compares the average change in GFR over three years between the two groups. I'm not sure how to do this in STATA. In SAS I using the following: PROC mixed data= habc.habclong covtest; class habcid ckd1 time; model gfr = ckd1*time/solution ; repeated time/type=un subject=habcid; estimate 'avg change/year between baseline and year 3 for grp 1' ckd1*time -0.333 0.333 0 0 0 0 ; estimate 'avg change/year between year 3 and year 10 for grp 1' ckd1*time 0 -0.143 0.143 0 0 0 ; estimate 'avg change/year between baseline and year 3 for grp 2' ckd1*time 0 0 0 -0.333 0.333 0 ; estimate 'avg change/year between year 3 and year 10 for grp 2' ckd1*time 0 0 0 0 -0.143 0.143 ; where inclusion=1; run; When I use the following STATA code: xi: xtmixed gfr totpa3cat##time if inclusion==1 /// || habcid: , noconstant residuals(uns, t(time)) nolog reml margins totpa3cat time totpa3cat##time if inclusion==1, contrast It does not give me the same information. It only gives me the mean GFR at each time point by CKD group. I can't put in the contrast here the same as I do it in SAS. Any advice? ---------------------------------------- > Date: Sat, 22 Sep 2012 12:11:52 -0400 > Subject: Re: st: Convert SAS code to STATA > From: jvverkuilen@gmail.com > To: statalist@hsphsun2.harvard.edu > > On Sat, Sep 22, 2012 at 11:59 AM, Marquis Hawkins > <marquishawkins82@hotmail.com> wrote: > > Hi, > > > > Does anyone know how to convert this SAS code to STATA? > > > > > > PROC mixed data= habc.habclong covtest; > > class habcid ckd1 time; > > model gfr = ckd1*time/solution ; > > repeated time/type=un subject=habcid; > > estimate 'avg change/year between baseline and year 3 for grp 1' ckd1*time -0.333 0.333 0 0 0 0 ; > > estimate 'avg change/year between year 3 and year 10 for grp 1' ckd1*time 0 -0.143 0.143 0 0 0 ; > > estimate 'avg change/year between baseline and year 3 for grp 2' ckd1*time 0 0 0 -0.333 0.333 0 ; > > estimate 'avg change/year between year 3 and year 10 for grp 2' ckd1*time 0 0 0 0 -0.143 0.143 ; > > where inclusion=1; > > run; > > PROC MIXED would go over to -xtmixed-. > > The "estimate" commands would be post-estimation calls to -margins-. > > The "class" statement would be done using Stata factor commands (i., > etc.) or -xi-. > > "Repeated" specifies the random structure. That's the part you'll have > to do a little work to map to the right specification but it looks > like you wanted an unstructured covariance matrix and that should be > pretty straightforward to do. > > > -- > JVVerkuilen, PhD > jvverkuilen@gmail.com > > "Out beyond ideas of wrong-doing and right-doing there is a field. > I'll meet you there. When the soul lies down in that grass the world > is too full to talk about." ---Rumi > * > * 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/

**Follow-Ups**:**Re: st: Convert SAS code to STATA***From:*"JVerkuilen (Gmail)" <jvverkuilen@gmail.com>

**References**:**st: Convert SAS code to STATA***From:*Marquis Hawkins <marquishawkins82@hotmail.com>

**Re: st: Convert SAS code to STATA***From:*"JVerkuilen (Gmail)" <jvverkuilen@gmail.com>

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