[R] how to specify starting values in varIdent() of lme()

[toby909 at gmail.com]

I was reading the help but just did not get how to specify starting values for 
varIdent() of the lme() function, although I managed to do it for corSymm().

Do I specify the values just as they are printed out in an output, like c(1, 
1.3473, 1.0195). Or do I need to take the residual and multiply it with these 
like c(0.2235, 0.2235*1.3473, 0.2235*1.0195)
or any other form that I dont know of?

Thanks Toby





Linear mixed-effects model fit by REML
  Data: dtaa
        AIC       BIC   logLik
   -788.783 -692.5656 409.3915

Random effects:
  Formula: ~timef - 1 | orgid
  Structure: General positive-definite, Log-Cholesky parametrization
          StdDev     Corr
timef1   0.04398482 timef1 timef2
timef2   0.07910354 1
timef3   0.03648411 1      1
Residual 0.22350583

Correlation Structure: General
  Formula: ~1 | orgid/id
  Parameter estimate(s):
  Correlation:
   1     2
2 0.487
3 0.597 0.440
Variance function:
  Structure: Different standard deviations per stratum
  Formula: ~1 | time
  Parameter estimates:
        1        2        3
1.000000 1.347341 1.019529
Fixed effects: score ~ timef - 1
             Value   Std.Error   DF   t-value p-value
timef1 -0.3846847 0.007627811 4421 -50.43186       0
timef2 -0.2727646 0.012012786 4421 -22.70619       0
timef3 -0.3961244 0.007180147 4421 -55.16939       0
  Correlation:
        timef1 timef2
timef2 0.735
timef3 0.746  0.670

Standardized Within-Group Residuals:
        Min         Q1        Med         Q3        Max
-1.4659548 -0.5982929 -0.4096429  0.3101507  4.0911728

Number of Observations: 4515
Number of Groups: 92