如何在 R 中使用 plot 分类模式？

Question

Year        Dist        Ratio
<int>       <chr>       <dbl>
2018        A       1.576287
2018        B       3.487632
2018        C       2.827363
2019        A       2.176387
2019        B       1.326874
2019        C       1.728745

ggplot(data = df) +
  geom_line(aes(x = Year, y = Ratio)) 

but it shown

How can I plot similar pattern to the picture?

Answer 1

Are you after this?

ggplot(data = df) +
  geom_line(aes(x = Year, y = Ratio, color = Dist))

---

Or following @Konrad Rudolph' comment, we can convert Year into date type, eg,

ggplot(data = df) +
  geom_line(aes(x = as.Date(paste0(Year,"-01-01")), y = Ratio, group = Dist))

Answer 2

You can use this code:

library(tibble)
library(ggplot2)
df <- tribble(
~Year,        ~Dist,        ~Ratio,
2018, "A", 1.576287, 
2018, "B", 3.487632, 
2018, "C", 2.827363, 
2019, "A", 2.176387, 
2019, "B", 1.326874, 
2019, "C", 1.728745)

df$Year <- as.factor(df$Year)
df$Dist <- as.factor(df$Dist)
ggplot(data = df) +
  geom_line(aes(x = Dist, y = Ratio, colour = Year, group = Year)) +
  theme_classic()

Answer 3

In the linked image, the x-axis is categorical , and is so because the variable passed in aes(x =...) is a character vector or factor vector.

In your case, Year is numerical, hence the x-axis is interpreted as a nominal scale, as you can have 2018, 2018.9, 2018.999, 2019.0, 2020 (never mind that it doesn't necessarily makes sense in your case).

To force the x-axis, convert the Year -variable into a factor, as such:

ggplot(data = df) +
  geom_line(aes(x = as.factor(Year), y = Ratio)) +
  labs(x="Year")