Problems getting results of MatchIt with rpy2 / How to debug R function with rpy2?

Question

I wasn't able to reproduce this in an MWE. I was using this code in the past and it worked. Some might have changed since then.

There is no error. The problem is that get_balance is of NoneType. The self build R function did not return something.

get_balance = robjects.r('''f <- function(match_out) {
        result <- summary(match_out)$sum.all
        result <- as.data.frame(result)
        return(result)
    }
    ''')

balance = get_balance(match_result)

I am not well experienced with R. So I don't know how to debug this or to add some debug helper lines in that R code.

I could break it into several steps e.g. robjects.r['summary']. But I don't know how to "translate" the $sum.all into Python.

I don't know where to start.

Answer 1

The R code f <- function() {} does not return anything. It declares a function and binds it to the symbol f in the evaluation frame / environment.

You can either do:

get_balance = robjects.r('''function(match_out) {
    result <- summary(match_out)$sum.all
    result <- as.data.frame(result)
    return(result)
}
''')

or

get_balance = robjects.r('''f <- function(match_out) {
    result <- summary(match_out)$sum.all
    result <- as.data.frame(result)
    return(result)
}
f
''')