R help - Feb 2013 - total indirect effects in structural equation modeling using lavaan

Hi all,

I am using package lavaan and have created a structural equation model with
two exogenous and seven endogenous variables with the following
relationships

#specify the model
m1 = '     # regressions
            D ~ ma + hs + b4 + b5 +  b15 + b16
            ma ~ hs + b4 + b5 + b15 + b16
            hs ~ b4 + b5 + b15 + b16

            b4 ~ el + la
            b5 ~ el + la
            b15 ~ el + la
            b16 ~ el + la

        #(residual) variances and covariances

            b4 ~~ b5
            b4 ~~ b15
            b4 ~~ b16
            b5 ~~ b15
            b5 ~~ b16
            b15 ~~ b16
    '

# fit the model
fit.m1 = sem(m1, data=x)

# summary result with standardised coefficients and r^2
summary(fit.m1, standardized = TRUE, rsq=TRUE)
#

My question.......I would like to calculate the total indirect effects of
all variables on the right-hand-side of the regression eqn's so that i can
work out the total effect (indirect effects + direct effect)

I know the direct effect and i can calculate the total indirect effects by
hand but i was wondering if there is a function that can calculate this?

Many thanks

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On 02/21/2013 03:59 PM, Marios wrote:
> My question.......I would like to calculate the total indirect effects of
> all variables on the right-hand-side of the regression eqn's so that i
can
> work out the total effect (indirect effects + direct effect)
>
> I know the direct effect and i can calculate the total indirect effects by
> hand but i was wondering if there is a function that can calculate this?
In the current version of lavaan (0.5-11), there is no function that 
will compute all possible indirect/total effects automatically.

What you can do is to label the coefficients, and then use the ':=' 
operator to define the total/indirect effects that you are interested 
in. Next, you could use se="boot" to get a bootstrap based SE.

See the lavaan paper (http://www.jstatsoft.org/v48/i02/) section 7.4 for 
an example.

Yves.