Calendar Plot using ggplot2

ggplot2.calendar

require(lubridate)
require(plyr)
require(ggplot2)
theme_set(theme_bw())

# create random dataset
df <- data.frame(DATETIME = ymd("2000-01-01") + ddays(runif(100)*365*5))

# compute day/month columns
df <- mutate(df,
             YEAR=factor(year(DATETIME)),
             MONTH=factor(month(DATETIME, label=TRUE, abbr=TRUE)),
             WEEKDAY=factor(wday(DATETIME, label=TRUE, abbr=TRUE), levels=c('Sun', 'Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat')),
             MONTHDAY=mday(DATETIME),
             MONTH_FIRST_WDAY=wday(ymd(paste(YEAR,MONTH,1,sep='-'))),
             MONTHWEEK=factor(floor((mday(DATETIME)+MONTH_FIRST_WDAY-2)/7)+1, levels=c(1:6))
)

# plot
ggplot(df, aes(MONTHWEEK, WEEKDAY)) + 
  geom_tile(fill='black', color='white') +
  facet_grid(YEAR~MONTH, drop=FALSE) + 
  labs(x="Week of the Month", y="Day of the Week") +
  scale_y_discrete(drop=FALSE, limits = rev(levels(df$WEEKDAY))) +
  scale_x_discrete(drop=FALSE)