grouped bar plot with ggplot2 geom_bar is plotting proportions not counts

Question

I'm trying to plot a grouped bar plot (x, y by another variable) but I'm getting a proportions graph (0-1) instead of counts, with all the bars going to 1. I'm confused because the code is seems correct (using stat identity and position dodge)

I've tried factoring the variables, doesn't work. The data frame is in long form.

ggplot(supra.long, aes(condition, measurement, fill = MODE)) +
  geom_bar(position = 'dodge', stat = "identity")

Got the same result when I plotted this small portion of the data:

 A tibble: 6 x 3

condition measurement MODE 
  <chr>           <dbl> <chr>

INTACT              1 US   
INTACT              0 US   
INTACT              1 US   
FT                  0 MRI  
FT                  1 MRI  
FT                  0 MRI

I'm expecting a plot of counts on the y axis, but the bars all go to 1 on a proportion scale.

I want to plot the counts of value =1 for measurement. I tried converting to a chr, no change. — JuanTamad
I think that's where the problem is. How does it count the positive (measurement = 1) values? Or can it. How do I plot this data? Create a separate dataset of only the positive values, I suppose. — JuanTamad

olorcain olorcain · Accepted Answer · 2019-04-16T12:30:34

I'd probably either summarise the data before I plot it and use the "identity" stat.

library(dplyr)
condition <- c("INTACT","INTACT","INTACT","FT","FT","FT")
measurement <- c(1,0,1,0,1,0)
MODE <- c("US","US","US","MRI","MRI","MRI")
supra.long <- data.frame(condition, measurement, MODE) %>%
  group_by(condition, MODE) %>%
  summarise(count = sum(measurement))

ggplot(supra.long) +
  geom_bar(aes(x=condition, y=count, fill = MODE), position = 'dodge', stat = "identity")

Or I would filter out the zeros and use the "count" stat.

supra.long <- data.frame(condition, measurement, MODE) %>% filter(measurement > 0)
ggplot(supra.long) +
  geom_bar(aes(x=condition,fill = MODE), position = 'dodge', stat = "count")

Hope that helps.

grouped bar plot with ggplot2 geom_bar is plotting proportions not counts

1 Answers