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rggplot2
Rahil Vora
Rahil Vora

Reputation: 145

ggplot2() fix x-axis for melt variable

I am plotting multiple vectors in one graph with ggplot2. I have the following dataframe

Array 1 2 3 4 5 6 7 8 9 10
Arr1 0.1 0.1 0.1 0.2 0.2 0.2 0.7 0.7 0.4 0.7
Arr2 0.6 0.6 0.6 0.1 0.1 0.1 0.1 0.1 0.5 0.1
Arr3 0.3 0.3 0.3 0.7 0.7 0.7 0.2 0.2 0.1 0.2
Arr4 0.4 0.6 0.7 0.2 0.1 0.3 0.4 0.5 0.3 0.9
B a a a b b b a a a b
C b b b a a b b a b a

So I melt the data to plot all vectors with horizontal stack bar, which is as follows:

df2<-df %>% 
  melt(id.vars = "Array") %>%
  mutate(variable = str_extract(variable, "[0-9]+")) %>%
  mutate(value = case_when(
    value == "a" ~ 1,
    value == "b" ~ 2, 
    TRUE ~ as.numeric(value)
  )) %>%
  mutate(variable = as.numeric(variable))
  
df2 %>% 
  ggplot(aes(x = Array, y = variable, group = Array, fill = value)) +
  geom_col() + coord_flip()

But the x-axis is not proper, the image shows that same number of a and b in vector B has different sizes, also last single element has bigger size than first three. The problem in x-axis is easier to detect with vector B and C then Arr.

When you look at df2 variable only has 1 to 10, I cannot figure out how there are more than 50 points on x - axis.

Graph

Upvotes: 1

Views: 267

Answers (1)

Xiang
Xiang

Reputation: 314

This is because each bar is stacking the y (variables). For each Array category, the bar is stacking from 1 to 10, the total is 1+2+...+10 = 55, that's why you see the x-axis is over 50. That's also the reason that B and C have different sizes for a and b. The first blue blocks for B and C are: (a, a, a) = (1+2+3) = 6 and (b, b, b) = (1+2+3) = 6, they have the same size. The second blue blocks for B and C are: (b, b ,b) = (4+5+6) = 15 and (a, a) = (4+5) =9, they have different sizes.

If you want the x-axis to have range between 1-10 and the B and C have same sizes for a and b. Set your y (variable) to be a vector of 1.

df2<-df %>% 
  melt(id.vars = "Array") %>%
  mutate(value = case_when(
    value == "a" ~ 1,
    value == "b" ~ 2, 
    TRUE ~ as.numeric(value)
  )) %>%
  mutate(variable = 1) # change to 1

Update legend: you can use scale_fill_continuous() to customize the legend text. Using the code below, you will get legend in the picture.enter image description here

df2 %>%
  ggplot(aes(x = Array, y = variable, group = Array, fill = value)) +
  geom_col() + 
  scale_fill_continuous(breaks = c(0.1, 1, 2), labels = c("0.1", "1 (=a)", "2 (=b)"))+
  coord_flip()

Upvotes: 0

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