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I am thinking how to convert string Date data of tall array format to Date and organise the ggplot by it in the x-axis by scale_x_date. Pseudocode motivated by Henrik's proposal

  1. Change string data format to as.Date, maybe something similar to the following in ggplot's parameter x = ...

    as.Date(time.data, format("%d.%m.%Y")

  2. Apply scale_x_date in ggplot with date_breaks("2 day")

Code with dummy data data3

library("ggplot2")
# For RStudio
options(device="pdf") # https://stackoverflow.com/questions/6535927/how-do-i-prevent-rplots-pdf-from-being-generated
filename.pdf <- paste0(getwd(), "/", "Rplots", ".pdf", sep = "")
pdf(file=filename.pdf)
# Dummy data
data3 <- structure(list(Time.data = c("16.7.2017", "15.7.2017", 
                                             "14.7.2017", "13.7.2017", "12.7.2017", "11.7.2017", "9.7.2017", 
                                             "7.7.2017", "6.7.2017", "5.7.2017", "4.7.2017", "3.7.2017", "2.7.2017", 
                                             "1.7.2017", "30.6.2017", "29.6.2017", "28.6.2017", "16.7.2017", 
                                             "15.7.2017", "14.7.2017", "13.7.2017", "12.7.2017", "11.7.2017", 
                                             "9.7.2017", "7.7.2017", "6.7.2017", "5.7.2017", "4.7.2017", "3.7.2017", 
                                             "2.7.2017", "1.7.2017", "30.6.2017", "29.6.2017", "28.6.2017", 
                                             "16.7.2017", "15.7.2017", "14.7.2017", "13.7.2017", "12.7.2017", 
                                             "11.7.2017", "9.7.2017", "7.7.2017", "6.7.2017", "5.7.2017", 
                                             "4.7.2017", "3.7.2017", "2.7.2017", "1.7.2017", "30.6.2017", 
                                             "29.6.2017", "28.6.2017"), variable = structure(c(1L, 1L, 1L, 
                                                                                               1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 
                                                                                               2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 
                                                                                               3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L
                                             ), .Label = c("ave_max", "ave", "lepo"), class = "factor"), 
                        value = c(69, 75, 83, 97, 101, 73, 77, 78, 98, 79, 78, 95, 
                                  70, 81, 78, 71, 72, 58, 59, 59, 58, 54, 56, 60, 60, 62, 58, 
                                  56, 63, 58, 58, 63, 58, 56, 48, 51, 51, 48, 48, 48, 52, 53, 
                                  52, 49, 48, 53, 50, 50, 54, 46, 47)), row.names = c(NA, -51L
                                  ), .Names = c("Time.data", "variable", "value"), class = "data.frame")

#Relevant part of the code based on Henrik's proposal, 
#rejected timestamp approach which output has wrongly shown x-axis label in Fig. 1
p <- ggplot(data3, aes(x = as.Date(Time.data, format = "%d.%m.%Y"), y = value, fill = variable)) + 
  geom_bar(stat='identity') + 
  theme(axis.text.x = element_text(angle = 90, hjust=1), 
        text = element_text(size=10)) +
  scale_x_discrete("Date") +
  scale_x_date(date_breaks = "2 days", date_labels = "%d.%m.%Y") 

print(p)
dev.off()

Output which I do not understand

Scale for 'x' is already present. Adding another scale for 'x', which will replace the existing scale.

Fig. 1 Output based on Henrik's proposal

enter image description here

Expected output: as such but with correct x-label there on the x-axis

OS: Debian 9
R: 3.4.0
RStudio: 1.0.143
Other sources: Date format for subset of ticks on time axis, scale_datetime shifts x axis, Time series plot gets offset by 2 hours if scale_x_datetime is used

Léo Léopold Hertz 준영
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1 Answers1

1

You have specified two different scales for the x axis, a discrete scale and a continuous date scale, presumably in an attempt to rename the label on the x axis. For this, xlab() can be used:

library(ggplot2)
ggplot(data3, aes(x = as.Date(Time.data, format = "%d.%m.%Y"), y = value, fill = variable)) +
  # use new geom_col() instead of  geom_bar(stat = "identity")
  # see http://ggplot2.tidyverse.org/articles/releases/ggplot2-2.2.0.html#stacking-bars
  geom_col() + 
  theme(axis.text.x = element_text(angle = 90, hjust=1), 
        text = element_text(size=10)) +
  # specify label for x axis
  xlab("Time.date") +
  scale_x_date(date_breaks = "2 days", date_labels = "%d.%m.%Y")

enter image description here

Alternatively, you can use the name parameter to scale_x_date():

ggplot(data3, aes(x = as.Date(Time.data, format = "%d.%m.%Y"), y = value, fill = variable)) + 
  geom_col() + 
  theme(axis.text.x = element_text(angle = 90, hjust=1), 
        text = element_text(size=10)) +
  scale_x_date(name = "Time.date", date_breaks = "2 days", date_labels = "%d.%m.%Y")

Addendum: Saving plots

If the intention is to save just one plot in a file you can add a call to ggsave() after the call to ggplot(), i.e.,

ggplot(...
ggsave("Rplots.pdf")

instead of

options(device="pdf") # https://stackoverflow.com/questions/6535927/how-do-i-prevent-rplots-pdf-from-being-generated
filename.pdf <- paste0(getwd(), "/", "Rplots", ".pdf", sep = "")
pdf(file=filename.pdf)
p <- ggplot(...
print(p)
dev.off()

According to help("ggsave")

ggsave() is a convenient function for saving a plot. It defaults to saving the last plot that you displayed, using the size of the current graphics device. It also guesses the type of graphics device from the extension.

Another issue is the creation of the file path. Instead of

filename.pdf <- paste0(getwd(), "/", "Rplots", ".pdf", sep = "")

it is better to use 

filename.pdf <- file.path(getwd(), "Rplots.pdf")

which constructs the path to a file from components in a platform-independent way.

Uwe
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