在ggplot中拟合对角线以绘制图形

Question

I have a data frame that looks like this

> wider_data
# A tibble: 12 x 6
   treat    FR    CC    HP Other x    
   <fct> <int> <int> <int> <int> <fct>
 1 1         0     2     5     3 0    
 2 1         2     1     5     1 1    
 3 1         3     5     3     2 2    
 4 1         0     2     4     1 3    
 5 1         1     2     4     1 4    
 6 1         0     2     4     0 5    
 7 2         4     1     4     2 0    
 8 2         1     5     2     0 1    
 9 2         4     0     1     4 2    
10 2         0     5     2     3 3    
11 2         0     3     4     1 4    
12 2         1     5     1     2 5  

I melt this data to

> m_wider_data <- melt(wider_data) #Using treat, levels, x as id variables
Using treat, x as id variables
> m_wider_data
   treat x variable value
1      1 0       FR     0
2      1 1       FR     2
3      1 2       FR     3
4      1 3       FR     0
5      1 4       FR     1
6      1 5       FR     0
7      2 0       FR     4
8      2 1       FR     1
9      2 2       FR     4
10     2 3       FR     0
11     2 4       FR     0
12     2 5       FR     1
13     1 0       CC     2
14     1 1       CC     1
15     1 2       CC     5
16     1 3       CC     2

(48 lines in total)

> class(m_wider_data$x)
[1] "factor"
> class(m_wider_data$value)
[1] "integer"

Then I plot 2 graphs (corresponding to the 2 levels of 'treat') using

plot_test <- m_wider_data %>%
  ggplot(aes(x = x, y = value, colour = variable, group = variable)) +
  facet_wrap(vars(treat), ncol = 2) +
  geom_point() +
  geom_line(aes(linetype=variable)) +
  geom_abline(slope = 1, intercept = 0) +
  labs(x = "X", y = "Y") +
  ggtitle('Table') +
  theme(legend.title=element_blank()) #turns of the legend title

However, the diagonal line ends up wrong

I want it to go through (0,0) (1,1) (2,2) (3,3) (4,4) (5,5).
In addition, I want cut the margins so that the graph area start so close to x=0 and y=0 as possible. I have tried to change x to a numeric variable and use

plot_test + 
  scale_x_continuous(breaks=c(0,1,2,3,4,5),limits = c(-0.05, 5.05)) +
  scale_y_continuous(breaks=c(0,1,2,3,4,5),limits = c(-0.05, 5.05))

But it is not working.

Is there a way to achieve this? Thank you in advance!

Answer 1

Maybe this is what you are looking for:

It's best to convert numeric. However, when converting a factor to a numeric you have to keep in mind that you first have to convert to a character. Otherwise your first category "0" becomes 1, your second category "1" becomes 2 and so on. Therefore always use as.numeric(as.character(x)) .

After this change your code should work fine. Nonetheless I made some small changes. I set the limits via coord_cartesain. And also I used the expand argument to scale_x/y_continuous to set the default expansion (= 5 percent) to 0. BTW: You don't need to add an extra ".05" to you limits as ggplot will expand your axes by default. (If you are fine with the default expansion you ould simply remove scale_x/y_continuous or if you want a different expansion try eg c(0.025, 0) which will expand the axis by 2.5 percent on both sides.)

library(ggplot2)
library(dpylr)

plot_test <- m_wider_data %>%
  ggplot(aes(x = as.numeric(as.character(x)), y = value, colour = variable, group = variable)) +
  facet_wrap(vars(treat), ncol = 2) +
  geom_point() +
  geom_line(aes(linetype=variable)) +
  geom_abline(slope = 1, intercept = 0) +
  labs(x = "X", y = "Y") +
  ggtitle('Table') +
  theme(legend.title=element_blank()) +
  coord_cartesian(xlim = c(0,5), ylim = c(0,5)) +
  scale_x_continuous(expand = c(0, 0)) +
  scale_y_continuous(expand = c(0, 0))
plot_test

DATA

m_wider_data <- read.table(text = "treat x variable value
1      1 0       FR     0
2      1 1       FR     2
3      1 2       FR     3
4      1 3       FR     0
5      1 4       FR     1
6      1 5       FR     0
7      2 0       FR     4
8      2 1       FR     1
9      2 2       FR     4
10     2 3       FR     0
11     2 4       FR     0
12     2 5       FR     1
13     1 0       CC     2
14     1 1       CC     1
15     1 2       CC     5
16     1 3       CC     2", header = TRUE)

m_wider_data$x <- factor(m_wider_data$x)

Answer 2

I think your problem is a result of x being a factor and not a number. It is best to perform that conversion early in the process.
Also, I have updated the matrix transformation using the more modern pivot_longer instead of melt

widedf<-read.table(header = TRUE, text="   treat    FR    CC    HP Other x    
1         0     2     5     3 0    
1         2     1     5     1 1    
1         3     5     3     2 2    
1         0     2     4     1 3    
1         1     2     4     1 4    
1         0     2     4     0 5    
2         4     1     4     2 0    
2         1     5     2     0 1    
2         4     0     1     4 2    
2         0     5     2     3 3    
2         0     3     4     1 4    
2         1     5     1     2 5")


library(tidyr)
#make the table long
df <- pivot_longer(widedf, -c("treat", "x"), names_to="variable", values_to="value")
#convert x from a character to an integer
df$x <- as.integer(as.character(df$x))


library(ggplot2)
plot_test <- df %>%
   ggplot(aes(x = x, y = value, colour = variable, group = variable)) +
   facet_wrap(vars(treat), ncol = 2) +
   geom_point() +
   geom_line(aes(linetype=variable)) +
   geom_abline(slope = 1, intercept = 0) +
   labs(x = "X", y = "Y") +
   ggtitle('Table') +
   theme(legend.title=element_blank()) #turns of the legend title
plot_test