What happens if you try [[j]]
? If this doesn't work I suggest posting some data so we can help (see here: FAQ: How to do a minimal reproducible example ( reprex ) for beginners)
library(DescTools)
dfs <- ls()[sapply(mget(ls(), .GlobalEnv), is.data.frame)]
for (j in 1:length(dfs)){
Gini(dfs[[j]]$value)
}