Check out my R package "npcausal" for nonparametric causal inference methods at: 

github.com/ehkennedy/npcausal

It includes functions for computing causal effect estimators that incorporate flexible machine learning based on the theory of influence functions and sample splitting. 

To load npcausal in R, simply run the commands:

install.packages("devtools")
library(devtools)
install_github("ehkennedy/npcausal")
library(npcausal)

Along with standard treatment effect estimators, npcausal can also implement methods from my other papers listed on the Research page.