labeling x-axis with dates in geom_line in ggplot2

Question

I want to make a time series plot for weekdays (ie excluding weekends and holidays): If I simply use ggplot with date on the x-axis and y on the y-axis the distance between a Monday and Tuesday will not be the same as the distance between Friday and Monday. There is a daily data set bellow with a date column.

df <- structure(list(PROCEDURE_DATO_DATO = structure(c(17533, 17534, 17535, 17536, 17539, 
                                                       17540, 17541, 17542, 17543, 17546, 
                                                       17547, 17548, 17549, 17550, 17553, 
                                                       17554, 17555, 17556, 17557, 17560), 
                                                     class = "Date"), 
                     Antal_akutte = c(17, 31, 22, 18, 25,
                                      26, 20, 20, 21, 19, 
                                      25, 26, 27, 14, 14, 
                                      39, 21, 23, 20, 13), 
                     Antal_besog = c(42L, 60L, 58L, 58L, 56L, 
                                     61L, 44L, 48L, 47L, 44L, 
                                     58L,60L, 58L, 45L, 38L, 
                                     73L, 49L, 50L, 53L, 40L), 
                     Andel = c(0.404761904761905, 0.516666666666667, 0.379310344827586, 
                               0.310344827586207, 0.446428571428571, 0.426229508196721, 
                               0.454545454545455, 0.416666666666667, 0.446808510638298, 
                               0.431818181818182, 0.431034482758621, 0.433333333333333, 
                               0.46551724137931, 0.311111111111111, 0.368421052631579, 
                               0.534246575342466, 0.428571428571429, 0.46, 0.377358490566038, 0.325)), 
                .Names = c("PROCEDURE_DATO_DATO", "Antal_akutte", "Antal_besog", "Andel"), 
                row.names = c(NA, -20L), class = c("tbl_df", "tbl", "data.frame"))

If I simply make a row_number then I loose the dates on the axis. How can I use the row number, but label the axis with the date column?

df %>% 
  mutate(row = row_number()) %>% 
  ggplot(aes(row, Antal_akutte)) +
  geom_line()

If I try to create a label with scale_x_continues I get an error:

data %>% 
  mutate(row = row_number(), 
         PROCEDURE_DATO_DATO = as.character(PROCEDURE_DATO_DATO)) %>%
  ggplot(aes(row, Antal_akutte)) +
    geom_line() +
    scale_x_continuous(labels = seq.Date(as.Date("2018-01-02"), as.Date("2018-12-31"), by = "q"))

Error in f(..., self = self) : Breaks and labels are different lengths

Answer 1

You can transform your data to an eXtensible time series (xts) object which makes work with time series pretty easy. Then use autoplot to plot the xts object using ggplot2:

# load libraries
library(ggplot2)
library(xts)

# create an xts object (an xts object is formed by the matrix of observations, ordered by an index of dates - in your case `df$PROCEDURE_DATO_DATO`)
df_xts <- xts(df[,-1], order.by =df$PROCEDURE_DATO_DATO)

# make the plot
autoplot(df_xts, geom="line") 

Let's plot a few observations including the first weekend from January:

> df_xts[3:6,]
           Antal_akutte Antal_besog     Andel
2018-01-04           22          58 0.3793103
2018-01-05           18          58 0.3103448
2018-01-08           25          56 0.4464286
2018-01-09           26          61 0.4262295

I'll use geom = "point" to clearly indicate the missing data points during the weekend.

autoplot(df_xts[3:6,], geom="point") :

Update: To plot without the weekend dates, your solution should work:

df <- df[3:6,] %>% mutate(row=row_number(), PROCEDURE_DATO_DATO=as.character(PROCEDURE_DATO_DATO))

ggplot(df, aes(row, Antal_akutte)) + geom_line() + scale_x_continuous(breaks = df$row, labels=df$PROCEDURE_DATO_DATO)