I got the same warning message using RStudio 1.2.1335 on Mac (R 3.6.1).
I installed XQuartz and now I get:
library(summarytools)
Registered S3 method overwritten by 'pryr':
method from
print.bytes Rcpp
system has no X11 capabilities, therefore only ascii graphs will be produced by dfSummary()
Warning message:
In fun(libname, pkgname) : couldn't connect to display ":0"
Any idea why it does this ?