[R] Extracting correlation in a nlme model

[Kenneth Roy Cabrera Torres]

Hi R users:

Is there a function to obtain the correlation within groups
from this very simple lme model?

> modeloMx1
Linear mixed-effects model fit by REML
  Data: barrag 
  Log-restricted-likelihood: -70.92739
  Fixed: fza_tension ~ 1 
(Intercept) 
   90.86667 

Random effects:
 Formula: ~1 | molde
        (Intercept) Residual
StdDev:    2.610052 2.412176

Number of Observations: 30
Number of Groups: 3 

I want to obtain \rho = \sigma_b^2 / (\sigma_b^2 + \sigma^2)

I know that I obtain \sigma_b^2 and \sigma^2 with

> VarCorr(modeloMx1)

molde = pdLogChol(1) 
            Variance StdDev  
(Intercept) 6.812374 2.610052
Residual    5.818593 2.412176

But, I want to know if I can obtain
\rho = 6.8123/(6.8123 + 5.8185) = 0.53934 straightforward.

Thank you for you help.

Kenneth