Calculation for background characteristic of data sets that were imputed by mice and matched by MatchThem I have performed multiple imputation in mice and created a dataset of 100 imputed data sets and then used MatchThem to perform propensity score matching.
I can assess the balance of matched data sets with the bal.tab function in the cobalt package, but I would also like to know the average background characteristics of the population after matching (for example, mean age of matched subjects). Please let me know if there are any useful functions or packages to compute the average background information of the multiple imputed data sets that were created mice and matched by MatchThem.

You can view means and standard deviations within each imputed dataset by requesting balance on all the imputed datasets and requesting the means be displayed. The code below does this:
bal.tab(m.out, which.imp = .all, disp = c("means", "sds"))

If you want a single number for each variable that describes the distribution of each covariate across all imputed datasets, there is none. There is no single distribution of age in the matched datasets; there are $M$ matched datasets and a different distribution of each covariate within each one. What value would you like to compute and display? If you have a suggestion feel free to submit an issue and I will look into implementing it. As far as I know, there are no standards for reporting this kind of value.
