I'm trying to make a formula and I got the error: $ operator not defined for this S4 class with R. First of all, what is a S4 class? What am I doing wrong
visual-c++-2008
default-selected
azure-application-gateway
svg-rect
blackberry
array-reduce
deno
vapor-fluent
deoptimization
flutter-font
babel-loader
hapi-fhir
real-time-systems
rounded-corners
dpkt
vcloud-director-rest-api
linkageerror
card
qmk-firmware
uitypeeditor
jest-junit
httprequest
inputbox
strtotime
pymel
pdf-reader
calabash-android
https-redirect
provisioning-profile
ios9.3
