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rdateplotjulian-date

Join year and julian day as a date column in R and plot it

I have some data with a column for the day of the year and another for year. As example, let's think in this dummy data:

temp <- rep(runif(730,15,40))
doy <- rep(c(1:365),2)
year <- c(rep(2015,365), rep(2016,365))

I would like to join doy and year as a date column (2015-365 format). Is it possible to deal with this date format? How ggplot or the basic function plot deal with it?

Solution

  • To convert a Julian date to a Date object use the %j format. For example:

    temp <- rep(runif(730,15,40))
doy <- rep(c(1:365),2)
year <- c("2015","2016")

jdate<-as.Date(paste(year, doy, sep="-"),"%Y-%j") 
df<- data.frame(jdate, temp)

library(ggplot2)
f<-ggplot(df, aes(x=jdate, y=temp))
f+ geom_point() + scale_x_date(date_breaks="6 week", date_labels="%Y-%j")