Plotting Year and Month in scatter plot R

Question

I have a dataset with Year and Month number that I am trying to plot against another variable, in this case "MEI". Here is a small sample of the data:

Year,   Month,  MEI,
1983,   5,  2.556,
1983,   6,  2.167,
1983,   7,  1.741,
1983,   8,  1.13,
1983,   9,  0.428,
1983,   10, 0.002,
1983,   11, -0.176,
1983,   12, -0.176,
1984,   1,  -0.339,
1984,   2,  -0.565,

Is there a way to make the x axis continuous over the years (Months-11,12,1,2). I tried:

plot(weather$Month, weather$MEI, main = 'Regression for MEI Each Month Over 16.5 Years', 
xlab = 'Month (From May 1983 to December 2008', ylab = 'MEI')

and I got this scatter plot.

Answer 1

One solution is to generate dates from the year/month values by adding "01" as the day. You can do that using dplyr::mutate . If you use ggplot2 for plotting, it will make formatting a date x-axis easier too.

library(dplyr)
library(ggplot2)

weather %>% 
  mutate(Date = as.Date(paste(Year, Month, "01", sep = "-"))) %>% 
  ggplot(aes(Date, MEI)) + 
  geom_point() + 
  scale_x_date(date_labels = "%b %Y")

Answer 2

You could convert the months and the year to a date and then plot the date against MEI :

weather$date <- as.Date(paste0(weather$Year, "-", weather$Month, "-01"))

plot(weather$date, weather$MEI, main = 'Regression for MEI Each Month Over 16.5 Years', 
    xlab = 'Month (From May 1983 to December 2008', ylab = 'MEI')