更改 x 轴刻度

Question

Good afternoon everyone,

I am having difficulties plotting a time series with ggplot. I have a time series with daily data from 2020-01-30 to 2020-10-22. When I plot the data with the following code, I get an x-axis, which is not at all readable:

plot_cases <- ggplot(NULL, aes(x= Date, y= Count)) +
  xlab("Time") + ylab("Number of Cases") +
  scale_y_continuous(limits=c(0, 2000)) +
  scale_x_discrete() +
  geom_line(data = P_cases_reduced_aggregated_female, aes(colour = P_cases_reduced_aggregated_female$Sex, group = 1)) +
geom_line(data = P_cases_reduced_aggregated_male, aes(colour = P_cases_reduced_aggregated_male$Sex, group = 1)) +
  scale_color_manual(values=c("#FF00FF", "#000FFF"))

Therefore, I would like to only have the abbreviation of the months represented such as "Apr", "Jul", "Oct". However, as I use the following code, I don't get any x-axis graduation anymore...

plot_cases <- ggplot(NULL, aes(x= Date, y= Count)) +
  xlab("Time") + ylab("Number of Cases") +
  scale_y_continuous(limits=c(0, 2000)) +
  scale_x_discrete(breaks = seq(as.Date("2020-01-30"), as.Date("2020-10-22"), by = "month")) +
  geom_line(data = P_cases_reduced_aggregated_female, aes(colour = P_cases_reduced_aggregated_female$Sex, group = 1)) +
geom_line(data = P_cases_reduced_aggregated_male, aes(colour = P_cases_reduced_aggregated_male$Sex, group = 1)) +
  scale_color_manual(values=c("#FF00FF", "#000FFF"))

As one of you a solution to this? I have checked the previous questions about scale_x_discrete but I still don't get how to do the relevant changes.

Thank you so much in advance.

Answer 1

Following the great advice of @AllanCameron and @r2evans first transform to date in x-axis to date and then use scale_x_date() . No output showed due to lack of data:

library(ggplot2)
#Code
plot_cases <- ggplot(NULL, aes(x= Date, y= Count)) +
  xlab("Time") + ylab("Number of Cases") +
  scale_y_continuous(limits=c(0, 2000)) +
  scale_x_date(date_labels="%B-%d",breaks = '7 days') +
  geom_line(data = P_cases_reduced_aggregated_female,
            aes(colour = P_cases_reduced_aggregated_female$Sex, group = 1)) +
  geom_line(data = P_cases_reduced_aggregated_male,
            aes(colour = P_cases_reduced_aggregated_male$Sex, group = 1)) +
  scale_color_manual(values=c("#FF00FF", "#000FFF"))+
  theme(axis.text.x = element_text(angle=90))