ferx_cor_matrix.RdConverts the parameter covariance matrix (already stored on the fit object) into a correlation matrix, making off-diagonal structure immediately visible. A correlation close to \(\pm 1\) between two parameters flags a structural identifiability problem in the model.
ferx_cor_matrix(fit)A ferx_fit object returned by ferx_fit.
Named correlation matrix (invisibly). Printed to the console.
ferx_estimates for SEs and \
ex <- ferx_example("warfarin")
fit <- ferx_fit(ex$model, ex$data, method = "gn", covariance = TRUE)
#> Warning: Model file [fit_options] sets `method = foce` but ferx_fit() argument overrides it with `gn`. The call-time value will be used.
#> Mu-referencing detected for: ETA_CL, ETA_KA, ETA_V
#> Negative IWRES autocorrelation detected (Durbin-Watson = 2.61, lag-1 r = -0.37).
#> Possible over-parameterisation or misspecified residual error model.
if (!is.null(fit$cov_matrix)) ferx_cor_matrix(fit)
#> TVCL TVV TVKA ETA_CL ETA_V ETA_KA PROP_ERR
#> TVCL 1.000 -0.746 -0.155 0.002 0.084 0.006 0.629
#> TVV -0.746 1.000 0.139 -0.001 -0.111 -0.006 -0.355
#> TVKA -0.155 0.139 1.000 0.000 -0.016 -0.041 -0.157
#> ETA_CL 0.002 -0.001 0.000 1.000 0.000 0.000 0.001
#> ETA_V 0.084 -0.111 -0.016 0.000 1.000 0.001 0.040
#> ETA_KA 0.006 -0.006 -0.041 0.000 0.001 1.000 0.006
#> PROP_ERR 0.629 -0.355 -0.157 0.001 0.040 0.006 1.000