Это то, что вы пытаетесь сделать?
# Make the Data Actually Useable
a<- c("1 8.2 JAN-1990", "2 5.3 JAN-1991",
"3 6.2 JAN-1992", "4 7.8 JAN-1993",
"5 6.7 JAN-1994") %>%
as_data_frame() %>%
separate(value, c("number", "temp", "month"), sep = " ") %>%
mutate(temp = as.numeric(temp),
# Now Convert the Date- Assuming First of Month?
month = lubridate::dmy(paste0("1-",month)))
# Base Way
plot(a$month, a$temp, xlab = "Month", ylab= "Temperature")
# Make the Chart in ggplot2
ggplot(a, aes(month, temp))+
geom_point()+
scale_x_date()