This is my code so far:
ggplot(df.summary, aes(Anthropogenic_Activity, FID_mean)) +
geom_col(fill = "blue", color = "black") +
geom_errorbar(aes(ymin = FID_mean-sd, ymax = FID_mean+sd), width = 0.2)+
df.summary$Anthropogenic_Activity=factor(df.summary$Anthropogenic_Activity,levels=c("L","M","H"))
But I keep getting the error "could not find function "+<-", what do you think the issue is?