[R] sem by variable x

[Daniel Caro]

Hi R users,

I am new in R. I would like to perform confirmatory factor analysis
for a data set of countries. My data are:

data <- read.csv("ses.raw", header = TRUE)
attach(data)
names(data)

[1] "idcntry" "momed"   "daded"   "dadocu"  "momocu"  "hompos"  "finan"


The country id is "idcntry", my model is "ses.model", and variables to
be included in the analysis are "momed"   "daded"   "dadocu"  "momocu"
 "hompos"  "finan" . How can I run

cfa<-sem(ses.model, cov(data[,2:7], nrow(data)))
summary(cfa)

by country? I am able to perform sem on all data by not by country. I tried

by(data[,2:7], idcntry, function(x) sem(ses.model, cov(data[,2:7]), nrow(data)))

but the output is the same for all countries.

Thank you,
Daniel