# Produce model syntax for various SEM software This function produces a model object or model syntax for SEM software based on a `semPlotModel-class` object. If the input is not a `"semPlotModel"` object the `semPlotModel` function is run on the input. This allows to create model syntax for one program based on the output of another program. Currently only the R packages 'lavaan' (Rosseel, 2012) and 'sem' (Fox, Nie & Byrnes, 2012) are supported. ```r semSyntax(object, syntax = "lavaan", allFixed = FALSE, file) ``` ## Arguments - `object`: A "semPlotModel" object or any of the input possibilities for `semPlotModel`. - `syntax`: A string indicating which syntax to be used for the output. Currently supported are `'lavaan'` and `'sem'`. - `allFixed`: Logical, should all parameters be fixed to their estimate. Useful for simulating data. - `file`: Path of a file the model should be written to. ## Returns A string containing the `lavaan` model syntax or a `"semmod"` object for the `sem` package. ## References Yves Rosseel (2012). lavaan: An R Package for Structural Equation Modeling. Journal of Statistical Software, 48(2), 1-36. URL http://www.jstatsoft.org/v48/i02/. John Fox, Zhenghua Nie and Jarrett Byrnes (2012). sem: Structural Equation Models. R package version 3.0-0. http://CRAN.R-project.org/package=sem ## Author(s) Sacha Epskamp ## See Also `semPlotModel` `semPlotModel-class` `semPaths` ## Examples ```r # MIMIC model, example 5.8 from mplus user guide: tryres <- try({ Data <- read.table("http://www.statmodel.com/usersguide/chap5/ex5.8.dat") }) if (!is(tryres,"try-error")){ names(Data) <- c(paste("y", 1:6, sep=""), paste("x", 1:3, sep="")) # Data <- Data[,c(7:9,1:6)] # Model: model.Lavaan <- 'f1 =~ y1 + y2 + y3 f2 =~ y4 + y5 + y6 f1 + f2 ~ x1 + x2 + x3 ' # Run Lavaan: library("lavaan") fit.Lavaan <- lavaan:::cfa(model.Lavaan, data=Data, std.lv=TRUE) # Obtain Lavaan syntax: model.Lavaan2 <- semSyntax(fit.Lavaan, "lavaan") # Run Lavaan again: fit.Lavaan2 <- lavaan:::lavaan(model.Lavaan2, data=Data) # Compare models: layout(t(1:2)) semPaths(fit.Lavaan,"std",title=FALSE) title("Lavaan model 1",line=3) semPaths(fit.Lavaan2, "std",title=FALSE) title("Lavaan model 2",line=3) # Convert to sem model: model.sem <- semSyntax(fit.Lavaan, "sem") # Run sem: library("sem") fit.sem <- sem:::sem(model.sem, data = Data) # Compare models: layout(t(1:2)) semPaths(fit.Lavaan,"std",title=FALSE) title("Lavaan",line=3) semPaths(fit.sem, "std",title=FALSE) title("sem",line=3) } ```

semSyntax function