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
writeablebitmap
twine-game-engine
picasa
max-msp-jitter
gcloudignore
parallel-for
sqlexception
pihole
virtualbox
user-defined-fields
onlyoffice
network-scan
scorm2004
user-administration
gulp-imagemin
mongoengine
flextable
rpt
sp-blitz
incallservice
tokenize
go-staticcheck
obsolete
bionic
speed-test
adsense
db-schema
cgcolorspace
glassfish-6
scons
