How to create a time scatterplot with R?

Question

The data are a series of dates and times.

date time
2010-01-01 09:04:43
2010-01-01 10:53:59
2010-01-01 10:57:18
2010-01-01 10:59:30
2010-01-01 11:00:44
…
         


        

Answer 1

The ggplot2 package handles dates and times quite easily.

Create some date and time data:

dates <- as.POSIXct(as.Date("2011/01/01") + sample(0:365, 100, replace=TRUE))
times <- as.POSIXct(runif(100, 0, 24*60*60), origin="2011/01/01")

df <- data.frame(
  dates = dates,
  times = times
)

Then get some ggplot2 magic. ggplot will automatically deal with dates, but to get the time axis formatted properly use scale_y_datetime():

library(ggplot2)
library(scales)
ggplot(df, aes(x=dates, y=times)) + 
  geom_point() + 
  scale_y_datetime(breaks=date_breaks("4 hour"), labels=date_format("%H:%M")) + 
  theme(axis.text.x=element_text(angle=90))

---

Regarding the last part of your question, on grouping by week, etc: To achieve this you may have to pre-summarize the data into the buckets that you want. You can use possibly use plyr for this and then pass the resulting data to ggplot.