In R, how can I extend a posixct timeseries axis beyond the end of the data

Question

The issue I am trying to fix is that one of my temperature loggers stopped early. This causes the x axis to be a different length to the others (See image Axis). I want to extend the axis to be the same for plotting next to each other with an end date/time of 2022-06-06 00:00:00.

Any suggestions on how to adjust this? I've pasted the main 3 chunks of code used to transform data and plot below. Thanks

SD1b <- SaxDeep1b
SD1b$datetime <- as.POSIXct(strptime(SD1b$datetime,format="%d/%m/%Y %H:%M",tz="Australia/Brisbane"))
head(SD1b)

SD1comb$datehour <- cut(as.POSIXct(SD1comb$datetime, format="%Y-%m-%d %H:%M:%S"),breaks="hour")
SD1hourlyT <-  aggregate(temp ~ datehour,SD1comb,mean)
head(SD1hourlyT)
SD1hourlyT$datehour <- as.POSIXct(strptime(SD1hourlyT$datehour,format = "%Y-%m-%d %H",
                                     tz="Australia/Brisbane"))
str(SD1hourlyT)

jpeg(file='SD1_temp.jpeg',width=19,height=10,res=1200,units="cm")
SD1temp <- ggplot(SD1hourlyT, aes(x = datehour, y = temp)) +
  geom_line(colour="black") +
  labs(x=element_blank(),y=expression("Temperature " ( degree*C)) ) +
  scale_x_datetime(date_breaks="1 month",date_labels = "%b") + #see ?strptime for labs
  scale_y_continuous(limits=c(23,33),breaks=c(23,25,27,29,31,33)) +
  theme_linedraw() +
  theme_minimal()+
    theme(axis.text.x  = element_text(colour="black",size=10),
        axis.title.x = element_text(color = "black", size=12),
        panel.grid.major = element_line(colour = "#d3d3d3"),
        panel.grid.minor = element_blank(),
        axis.text.y = element_text(colour="black",size=10),
        axis.title.y = element_text(color = "black", size=12)) +
  ggtitle("Saxon Deep 1")

We don't have your data so e.g. `SaxDeep1b` is not avalable to use and your code won't run...so we have no idea what's happening. Please share a minimal reproducible example https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example — socialscientist, Jul 25 '22 at 01:56
Hi, I don't think you should need to run the code as the question is more about formatting the axis. I included the code to demonstrate how the graphs were made and to highlight the POSIXct method as that seems to be the issue with changing lables — Justin B, Jul 25 '22 at 02:18
For us to troubleshoot possible approaches, we'll each have to come up with some fake data, try out solutions, and hope it matches the salient characteristics of your situation. Faster and less trouble if you can help us get oriented. — Jon Spring, Jul 25 '22 at 02:21
Similarly, if there is someone who also has the same question as you but does not have sufficient mastery to otherwise understand what you're doing, the example helps them understand through example. You'll find that pretty much every time you ask a question, people will want these examples on SO. — socialscientist, Jul 25 '22 at 02:27
Ok thanks guys, I am brand new to both R and SO (2 weeks in now) so will work on figuring out how to include this stuff. For now the answer provided has worked but I'll keep it in mind for the future — Justin B, Jul 25 '22 at 03:03

score 0 · Accepted Answer · answered Jul 25 '22 at 02:23

You can use the limits argument within scale_x_datetime to expand the scale.

library(dplyr)
library(ggplot2)
library(scales)
library(lubridate)

# Example data
df <- data.frame(date = as.POSIXct(
  c(
    "2016-12-05-16.25.54.875000",
    "2016-12-06-15.25.54.875000",
    "2016-12-08-14.25.54.875000",
    "2016-12-09-13.25.54.875000",
    "2016-12-09-12.25.54.875000",
    "2016-12-10-11.25.54.875000",
    "2016-12-10-10.25.54.875000",
    "2016-12-11-07.25.54.875000"
  ),
  format = "%Y-%m-%d-%H.%M.%S"
) ,
y = 1:8)

Default axis limits

The minimum and maximum values of date are the default limits, even if there is no label or tick mark at the spot.


ggplot(df, aes(x = date, y = y)) +
  geom_point() +
  scale_x_datetime(labels = date_format("%D"),
                   date_breaks = "2 day")

Expanded axis limits

We can expand the axis limits even to values not observed in our data. Once again, you'll need to adjust labels and tick marks if you want to scale them the same as well.

ggplot(df, aes(x = date, y = y)) +
  geom_point() +
  scale_x_datetime(
    labels = date_format("%D"),
    date_breaks = "2 day",
    limits = ymd_h("2016-12-05 00", "2016-12-20 23")
  )

Thank you, I had to change it to ymd_hms to match the format but this solution has worked. Appreciate it and will learn how to provide examples — Justin B, Jul 25 '22 at 03:04

In R, how can I extend a posixct timeseries axis beyond the end of the data

1 Answers1

Default axis limits

Expanded axis limits