| fixstart {psychonetrics} | R Documentation |
Attempt to Fix Starting Values
Description
This function attempts to fix starting values by comparing the analytic gradient to a numerically approximated gradient. Parameters with a difference between the analytic and numeric gradient that exceeds 'maxdiff' will be reduced by a factor of 'reduce' in each iteration until the average absolute difference between analytic and numeric gradients is lower than 'tol'. Only off-diagonal elements in omega, sigma, kappa, lowertri or rho matrices or any element in beta matrices are adjusted.
Usage
fixstart(x, reduce = 0.5, maxdiff = 0.1, tol = 0.01, maxtry = 25)
Arguments
x |
A 'psychonetrics' model |
reduce |
The factor with which problematic parameters are reduced in each iteration. |
maxdiff |
Maximum difference between analytic and numeric gradient to be considered problematic. |
tol |
Average absolute difference between analytic and numeric gradient that is considered acceptable. |
maxtry |
Maximum number of iterations to attempt to fix starting values. |
Author(s)
Sacha Epskamp