factor score formula in lavaan I would like get the factor scores of R/lavaan, achieved by a CFA model (single factor, 4 continuous indicators), by hand. Which is the formula (equation) as function of the observed indicators. In addition, I would like also get them by ordinal Likert indicators (again single factor). How I can get the continuous values that R/lavaan assigns to the Likert categories after the fit?
Many thanks in advance.
Best,

Welcome to CrossValidated Davide,
As Preston harkens to, there are different types of factor scores, and so you need to be specific about the kind you are wishing to compute--there isn't necessarily a generic factor score.
The seminal work in this area (IMO) is the paper, "Regression Among Factor Scores", by Skrondal and Laake. The authors discuss there being two approaches to calculating factor scores: the Regression method and the Bartlett method (this, I suspect, was the clarification Preston was after). Importantly, Skrondal and Laake demonstrate that each method is better/worse suited for when the factor score is to be used in a particular role (either as an explanatory or response variable) in some sort of substantive model.
Anyways, you'll find the formula for each in their paper.
References
Skrondal, A., & Laake, P. (2001). Regression among factor scores. Psychometrika, 66(4), 563-575.
