How to plot a start and end point for geom_line when data is in the same column

Question

I am creating a representation of a hospital observation chart in ggplot as part of a project.

I am having some difficulty identifying how to plot a vertical geom_line between the systolic blood pressure and diastolic blood pressure values when the data is held in one column. This is a standard way to represent blood pressure in written notation.

I have plotted the points as symbols in a ggplot using geom_point I now need to link the blood pressure values within each time point.

My ggplot code is as follows:

obschart <- obs %>% ggplot() +
  geom_point(aes(x=clinical_event_end_date_time, y=value, shape=point_shape))+
  ylab(label = "Value") +
  xlab(label = "Date / Time of observation")

My data is:

clinical_event,value,clinical_event_end_date_time,point_shape  
Diastolic Blood Pressure,71,02/01/2019 02:24,triangle down  
Diastolic Blood Pressure,76,02/01/2019 04:22,triangle down  
GCS Total,14,02/01/2019 02:24,square plus  
GCS Total,14,02/01/2019 03:42,square plus  
GCS Total,15,02/01/2019 04:22,square plus  
Heart Rate Monitored,48,02/01/2019 02:24,circle filled  
Heart Rate Monitored,56,02/01/2019 03:42,circle filled  
Heart Rate Monitored,62,02/01/2019 04:22,circle filled  
NEWS Total,2,02/01/2019 04:22,square cross  
NEWS Total,4,02/01/2019 02:24,square cross  
Peripheral Pulse Rate,48,02/01/2019 02:24,circle filled  
Peripheral Pulse Rate,56,02/01/2019 03:42,circle filled  
Peripheral Pulse Rate,62,02/01/2019 04:22,circle filled  
Respiratory Rate,16,02/01/2019 04:22,cross  
Respiratory Rate,17,02/01/2019 03:42,cross  
Respiratory Rate,18,02/01/2019 02:24,cross  
SpO2,95,02/01/2019 02:24,circle cross  
SpO2,95,02/01/2019 04:22,circle cross  
SpO2,96,02/01/2019 03:42,circle cross  
Systolic Blood Pressure,126,02/01/2019 02:24,triangle  
Systolic Blood Pressure,133,02/01/2019 04:22,triangle

The expected output would be a vertical line between the Systolic and Diastolic blood pressure values at each time point.

I have been unable to identify how to select systolic for y and diastolic for yend.

@MarcoSandri post an answer here if you have one, not a link to a third-party site — camille

olorcain olorcain · Accepted Answer · 2019-05-09T11:43:31

I'd probably split the line data out to a new data frame using dplyr:

library(dplyr)
lines <- obs %>%
  filter(clinical_event %in% c("Diastolic Blood Pressure","Systolic Blood Pressure")) %>%
  select(-point_shape) %>%
  spread(key=clinical_event, value=value) %>%
  rename(dia=2,sys=3)

Then add the line data to the chart you already have:

ggplot() +
  geom_point(data = obs, aes(x=clinical_event_end_date_time, y=value, shape=point_shape))+
  geom_segment(data = lines, aes(x=clinical_event_end_date_time, xend=clinical_event_end_date_time,
                                 y=dia, yend=sys)) +
  ylab(label = "Value") +
  xlab(label = "Date / Time of observation")

How to plot a start and end point for geom_line when data is in the same column

1 Answers