Plots the effect of a variable in a model estimated with Firth Logit.
effect_logistf(var, obj, data, ...)A character string giving the name of the variable whose effect is to be generated.
An object of class logistf.
A data frame.
Other arguments to be passed down to the Effect
function.
An object of class eff that can be used with other functions
from the effects package.
The effect.logistf function calculates the effect (predicted
probabilities) of a variable in a Firth logit model estimated with the
logistf function. The function estimates the analogous glm.
It then replaces the coefficient vector in that model object with the Frith
logit coefficients. It also puts the variance-covariance matrix from the
Firth logit in the model object and uses a custom extractor function in the
Effect function to extract that variance-covariance matrix rather
than the one usually extracted with vcov. Note that variability and
confidence intervals for the effects will not be calculated using profile
likelihood as they are in the Firth logit, but will be calculated using the
appropriate variance-covariance matrix.