getF calculates minimum of the ML-fit-function from known fit indices
getF(effect, effect.measure, df = NULL, p = NULL, SigmaHat = NULL,
Sigma = NULL)
magnitude of effect
measure of effect, one of 'fmin','rmsea','agfi','gfi','mc'
model degrees of freedom
number of observed varaibles
model implied covariance matrix
population covariance matrix
Fmin