How to create a spaghetti plot in R using ggplot?

Question

I have a dataset that looks like this:

  Study_ID time_point value
1      100      Time1    15
2      100      Time2    50
3      100      Time3   120
4      200      Time1    20
5      200      Time2    35
6      200      Time3   150
7      300      Time1    35
8      300      Time2    67
9      300      Time3    95

Where each patient (Study_ID) has 3 rows for the 3 time-points (Time 1, Time 2, and Time 3), with a value for each.

I would like to create a spaghetti plot with time_point on the x-axis, and the value on the y-axis, with a line for each patient. My desired output would look something like this:

How can I go about doing this?

Reproducible data:

data<-data.frame(Study_ID=c("100","100","100","200","200","200","300","300","300"),time_point=c("Time1","Time2","Time3","Time1","Time2","Time3","Time1","Time2","Time3"),value=c("15","50","120","20","35","150","35","67","95"))

Answer 1

By using the group and color arguments within aes() you can then add the layers geom_point() and geom_line() to keep color and group together.

library(tidyverse)

data<-data.frame(Study_ID=c("100","100","100","200","200","200","300","300","300"),time_point=c("Time1","Time2","Time3","Time1","Time2","Time3","Time1","Time2","Time3"),value=c("15","50","120","20","35","150","35","67","95"))

ggplot(data, aes(time_point, value, group = Study_ID, color = Study_ID)) + 
  geom_point() + 
  geom_line()

^{Created on 2022-06-20 by the reprex package (v2.0.1)}