Как так? Или вы ищете что-то другое?
df <- data.frame("Group.1"=c("A","B","C"), "Value"=c(20,20,20),
"SMA2"=c(18.0, 17.0, 18.5), "SMA3" =c(16.667, 16.667, 14.333),
"SMA4"=c(15.25, 15.00, 14.50))
library(ggplot2)
library(tidyr)
df.g <- df %>%
gather(SMA, Value, -Group.1)
df.g$SMA <- factor(df.g$SMA, levels=c("Value", "SMA2", "SMA3", "SMA4"))
means <- df.g %>%
group_by(SMA) %>%
summarise(m=mean(Value))
ggplot(df.g, aes(x=SMA, y=Value, group=Group.1, colour=Group.1)) +
geom_line() +
geom_point(data=means, aes(x=SMA, y=m), inherit.aes = F)