R: connect points on a graph (ggplot2)

Question

Suppose I have data in the following form:

library(ggplot2)

Data <- data.frame(
    
    "ID" = c("ABC111", "ABC111", "ABC111", "ABC111", "ABC112", "ABC112", "ABC112", "ABC113", "ABC113", "ABC114", "ABC115"),
"color" = c("red", "red", "red", "red", "blue", "blue", "blue", "green", "green", "black", "yellow"),
    "start_date" = c("2005/01/01", "2006/01/01", "2007/01/01", "2008/01/01", "2009/01/01", "2010/01/01", "2011/01/01", "2012/01/01", "2013/01/01", "2014/01/01", "2015/01/01"),
    "end_date" = c("2005/09/01", "2006/06/01", "2007/04/01", "2008/05/07", "2009/06/01", "2010/10/01", "2011/12/12", "2013/05/01", "2013/06/08", "2015/01/01", "2016/08/09")
)

Data$ID = as.factor(Data$ID)
Data$color = as.factor(Data$color)

Now what I want to do is for each row, plot the start_date and the end_date ... and then connect them with a straight line. I believe this can be done with geom_line() in ggplot2.

I want something that looks like this:

I tried using the following code:

q <- qplot(start_date, end_date, data=Data)
q <- q + geom_line(aes(group = ID))
q

But the graph looks completely different than what I expected.

Can anyone please show me what I am doing wrong?

Thanks

hello! the y-axis in this plot is meaningless ... it would be nice if the lines could be "staked" in the order of they appear in. is this possible to do? thanks — stats_noob, Dec 03 '20 at 04:42

Liman · Answer 1 · 2020-12-03T05:51:53.943

2

Does the following work for you?

ggplot(data = Data, aes(start_date, end_date, color = ID))+
  geom_line(aes(group = ID))+
  geom_point()

or maybe geom_segment ?

# Adding x and y coordinates for geom_segment
Data$x <- as.character(as.Date(Data$start_date) + (as.Date(Data$end_date) - as.Date(Data$start_date)))
Data$y <- 1:nrow(Data)

ggplot(data = Data, aes(x, y, colour = ID))+
  geom_segment(aes(xend = start_date, yend = end_date))

edited Dec 03 '20 at 05:51

answered Dec 03 '20 at 04:09

Liman

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12

hello! thank you for your reply. not exactly - I would like all the lines to be horizontal. and each line is just made of two points (from that row). is this possible to do? – stats_noob Dec 03 '20 at 04:41
1

Then, you may not have the right data. You are probably looking for something like `geom_segment`, in which case you need to provide further information about `x` and `y` axis. check if my edits can help you. – Liman Dec 03 '20 at 05:51

score 1 · Accepted Answer · answered Dec 03 '20 at 16:17

Here's a solution using the tidyverse package. I used the number of each row in the original data as the y-axis values in the plot. As these values are meaningless, I removed the y-axis title, labels and ticks from the plot.

library(tidyverse)

Data %>%
  # Number each row in its order of appearance, 
  # save this numbers in a new column named order
  rowid_to_column("order") %>%
  # Change data from wide to long format
  pivot_longer(cols = c(start_date, end_date),
               names_to = "date_type",
               values_to = "date") %>%
  # Ggplot, use date as x, order as y, ID as col and order as group
  ggplot(aes(x = date, 
             y = order,  
             col = ID, 
             group = order)) +
  # Draw points
  geom_point()+
  # Draw lines
  geom_line() +
  # Maybe you want to remove the y axis title, text and ticks
  theme(axis.title.y = element_blank(),
        axis.text.y = element_blank(),
        axis.ticks.y = element_blank(),
        # I added a vertical format to the x axis labels 
        # it might easier to read this way
        axis.text.x = element_text(angle = 90, vjust = 0.5))

R: connect points on a graph (ggplot2)

2 Answers2

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