Dear R users, Version 2.1-1 of the sem package, for structural equation modeling, is now on CRAN.
Unlike version 2.0-0, which was a major overhaul of the package, version 2.1-1 just sprinkles some syntactic sugar on it, introducing the specifyEquations() and cfa() functions; specifyEquations() supports model specification in equation (rather than path) format, and cfa() facilitates compact specification of simple confirmatory factor analysis models. For example, from ?sem, the Duncan, Haller, and Portes peer-influences model can now be specified as model.dhp.1 <- specifyEquations(covs="RGenAsp, FGenAsp") RGenAsp = gam11*RParAsp + gam12*RIQ + gam13*RSES + gam14*FSES + beta12*FGenAsp FGenAsp = gam23*RSES + gam24*FSES + gam25*FIQ + gam26*FParAsp + beta21*RGenAsp ROccAsp = 1*RGenAsp REdAsp = lam21(1)*RGenAsp # to illustrate setting start values, not necessary here FOccAsp = 1*FGenAsp FEdAsp = lam42(1)*FGenAsp and the Wheaton alientation model as model.wh <- specifyEquations() Anomia67 = 1*Alienation67 Powerless67 = lamby*Alienation67 Anomia71 = 1*Alienation71 Powerless71 = lamby*Alienation71 Education = 1*SES SEI = lambx*SES Alienation67 = gam1*SES Alienation71 = gam2*SES + beta*Alienation67 V(Anomia67) = the1 V(Anomia71) = the1 V(Powerless67) = the2 V(Powerless71) = the2 V(SES) = phi C(Anomia67, Anomia71) = the5 C(Powerless67, Powerless71) = the5 Similarly, the following are equivalent specifications of a CFA model for the Thurstore mental-tests data: (1) in CFA format: mod.cfa.thur.c <- cfa() FA: Sentences, Vocabulary, Sent.Completion FB: First.Letters, 4.Letter.Words, Suffixes FC: Letter.Series, Pedigrees, Letter.Group cfa.thur.c <- sem(mod.cfa.thur.c, R.thur, 213) summary(cfa.thur.c) (2) in equation format: mod.cfa.thur.e <- specifyEquations(covs="F1, F2, F3") Sentences = lam11*F1 Vocabulary = lam21*F1 Sent.Completion = lam31*F1 First.Letters = lam42*F2 4.Letter.Words = lam52*F2 Suffixes = lam62*F2 Letter.Series = lam73*F3 Pedigrees = lam83*F3 Letter.Group = lam93*F3 V(F1) = 1 V(F2) = 1 V(F3) = 1 cfa.thur.e <- sem(mod.cfa.thur.e, R.thur, 213) summary(cfa.thur.e) (3) in path format: mod.cfa.thur.p <- specifyModel(covs="F1, F2, F3") F1 -> Sentences, lam11 F1 -> Vocabulary, lam21 F1 -> Sent.Completion, lam31 F2 -> First.Letters, lam41 F2 -> 4.Letter.Words, lam52 F2 -> Suffixes, lam62 F3 -> Letter.Series, lam73 F3 -> Pedigrees, lam83 F3 -> Letter.Group, lam93 F1 <-> F1, NA, 1 F2 <-> F2, NA, 1 F3 <-> F3, NA, 1 As usual, I'd be grateful for comments, suggestions, and bug reports. Best, John -------------------------------- John Fox Senator William McMaster Professor of Social Statistics Department of Sociology McMaster University Hamilton, Ontario, Canada http://socserv.mcmaster.ca/jfox _______________________________________________ R-packages mailing list r-packa...@r-project.org https://stat.ethz.ch/mailman/listinfo/r-packages ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
