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
elastic-load-balancer
dropout
sslsocketfactory
content-management-system
klocwork
array-walk
cockroachcloud
f#-data
color-theory
splunk-dbconnect
scripting
coroutineworker
properties
factory-method
python-3.7
krb5.ini
clojure-core.logic
static-analysis
google-lyra
scopeguard
dbghelp
pyotherside
fctb
drawingcontext
yql
cypress-clock
kotlin-native
houghlinesp
gltf
rootview
