Question about ggplot2 bar graph transformation method

Question

I wanted the barplot to appear in two forms, so I created repeated data and used it as an input. So I used the data in the form below.

I put the data in the form above and wrote the following code to use it.

Select <- "Mbp"

if(Select == "Mbp"){
  Select <- "Amount of sequence (Mbp)"
} else if (Select == "Gbp"){
  Select <- "Amount of sequence (Gbp)"
}


ggplot(G4, aes(x = INDV, y = Bp, fill = Group)) + theme_light() +
  geom_bar(stat = 'identity', position = 'dodge', width = 0.6) + coord_flip() + 
  scale_x_discrete(limits = rev(unname(unlist(RAW_TRIM[1])))) +
  scale_fill_discrete(breaks = c("Raw data","Trimmed data"))+
  scale_y_continuous(labels = scales::comma, position = "right") +
  theme(axis.text = element_text(colour = "black", face = "bold", size = 15)) + 
  theme(legend.position = "bottom", legend.text = element_text(face = "bold", size = 15),
        legend.title = element_blank()) + ggtitle(Select) + xlab("") + ylab("") + 
  theme(plot.title = element_text(size = 25, face = "bold", hjust = 0.5))

enter image description here

Then I can get a plot like the one below, where I want the red graph to be on top of the green graph. I also tried changing the order of the data, and several sites such as the Internet and Stack Overflow provided solutions and used them, but not a single solution was able to solve them.

If you know a solution, please let me know how to modify the code or change the data. thank you.

Not entirely clear on what you're asking. Does replacing `position = "dodge"` with `position = "stack"` inside `geom_bar()` give you what you're after? — Maurits Evers, Jun 22 '22 at 01:14
It would help if you provided a small [reproducible and representative dataset](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example). As plain text, not images - we cannot copy/paste data from an image. If you included 1 raw and 1 trimmed value for two individuals, that would be enough. — neilfws, Jun 22 '22 at 01:18

score 1 · Accepted Answer · answered Jun 22 '22 at 02:10

You seem to be asking more than one question at once here, but the main one is: why do the bars for Raw appear under those for Trimmed? The short answer is: factor levels and the behaviour of coord_flip().

Let's make a toy dataset:

library(tidyverse)
G4 <- data.frame(INDV = c("C_01", "C_01", "C_41", "C_41"), 
                 Group = c("Raw data", "Trimmed data", "Raw data", "Trimmed data"), 
                 Bp = c(200, 100, 500, 400))

A simple dodged bar chart. Note that Raw comes before Trimmed, because R is before T in the alphabet:

G4 %>% 
  ggplot(aes(INDV, Bp)) + 
  geom_col(aes(fill = Group),
           position = "dodge")

Now we coord_flip:

G4 %>% 
  ggplot(aes(INDV, Bp)) + 
  geom_col(aes(fill = Group), 
           position = "dodge") + 
  coord_flip()

This has the effect of reversing the variables, so Raw is now below Trimmed.

We can fix that by altering factor levels. As there are only two groups we can just reverse them using fct_rev() from the forcats package:

G4 %>% 
  ggplot(aes(INDV, Bp)) + 
  geom_col(aes(fill = fct_rev(Group)), 
  position = "dodge") + 
  coord_flip()

The bar for Raw is now on top but unfortunately, the colours are now reversed so that Raw bars are green. We can fix that using scale_fill_manual():

G4 %>% 
  ggplot(aes(INDV, Bp)) + 
  geom_col(aes(fill = fct_rev(Group)), 
           position = "dodge") + 
  coord_flip() + 
  scale_fill_manual(values = c("#00BFC4", "#F8766D"))

Now the Raw bars are on top, and they are red.

Question about ggplot2 bar graph transformation method

1 Answers1