[R] mixed effect model (multilevel)

Hi, I have a problem with mixed effect model (multilevel). My model that is written in following formulation using the lme4 package and Zelig package: mylogit- lmer(OVERFLOW ~ ALTEZZA + INTENSITA + ( 1 | CODICE), family= binomial(link = probit),data = dati) OVERFLOW can be 0 or 1 and represents

[R] Ordered probit model -marginal effects and relative importance of each predictor-

Hi, I have a problem with the ordered probit model -polr function (library MASS). My independent variables are countinuos. I am not able to understand two main points: a) how to calculate marginal effects b) how to calculate the relative importance of each independent variables If required i