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rggplot2posixct

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

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")
Solution

  • 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")
  )