How do you show explained variation in cforest?

I'm trying to run a cforest model in R with continuous and categorical variables. When I tried this in randomForest, the explained variation was ok, but there was a large bias towards continuous variables. Therefore I switched to cforest, using the codes provided by Strobl et al.

This was my code:

my_cforestcontrol <- cforest_control(teststat="quad", testtype="Univ", mincriterion=0,
ntree=2000, replace=F)
my_cforest <- cforest(CSBUZZ ~ ., data=all, controls=my_cforestcontrol)
myvarimp <- varimp(my_cforest)


However, if I put print(my_cforest) or just my_cforest, the resulting summary doesn't give the percentage of variance explained. Is there any way I can get that information? I've tried several formula and the R help guide, but I couldn't find it anywhere.

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