如何 plot 两个 Y 轴刻度相同但值不同的图

Question

I have been trying to create a plot that shows the difference between two years of the same value. For comparison purposes I want the Y-axis to have the same breaks, however the data differs a lot between years. GGplot automatically adjusts the axis to this, is there any way to prevent this?

Current issue is visible in the picture. I would like both axis to range up to three hundred as I will eventually compare it to 2022 where the data also ranges higher than 2021.

# Plot for 2020
defplot20 <- ggplot(def20, aes(x=date, y=neerslagtekort)) +
  geom_line()  +  theme_classic() +
  theme(axis.text.x = element_text(angle = 90)) + 
  scale_x_date(date_breaks = "1 week", date_minor_breaks = "1 week",
               date_labels = "%d-%b", expand = c(0, 0)) +
  labs(y="Y", x="X") + ggtitle("2020") +
  scale_y_continuous(breaks = seq(0, 350, by = 25))

# Plot for 2021 
defplot21 <- ggplot(def21, aes(x=date, y=neerslagtekort)) +
  geom_line()  +  theme_classic() +
  theme(axis.text.x = element_text(angle = 90)) + 
  scale_x_date(date_breaks = "1 week", date_minor_breaks = "1 week",
               date_labels = "%d-%b", expand = c(0, 0)) +
  labs(y="Y", x="X") + ggtitle("2021") +
  scale_y_continuous(breaks = seq(0, 350, by = 25))

ggarrange(defplot20, defplot21)

Answer 1

As @wernor commented, merging the graphs in one graph seems a good option if you want to compare these graphs.

If you want to put them next to each other using ggarange your code is pretty close you just need to add the limits argument to your scale_y_continuous to force the axis scale to be the same:

# Plot for 2020
defplot20 <- ggplot(def20, aes(x=date, y=neerslagtekort)) +
  geom_line()  +  theme_classic() +
  theme(axis.text.x = element_text(angle = 90)) + 
  scale_x_date(date_breaks = "1 week", date_minor_breaks = "1 week",
               date_labels = "%d-%b", expand = c(0, 0)) +
  labs(y="Y", x="X") + ggtitle("2020") +
  scale_y_continuous(limits = c(0, 350), breaks = seq(0, 350, by = 25))

# Plot for 2021 
defplot21 <- ggplot(def21, aes(x=date, y=neerslagtekort)) +
  geom_line()  +  theme_classic() +
  theme(axis.text.x = element_text(angle = 90)) + 
  scale_x_date(date_breaks = "1 week", date_minor_breaks = "1 week",
               date_labels = "%d-%b", expand = c(0, 0)) +
  labs(y="Y", x="X") + ggtitle("2021") +
  scale_y_continuous(limits = c(0, 350), breaks = seq(0, 350, by = 25))

ggarrange(defplot20, defplot21)

Be aware! When using scale_y_continuous(limits = c(), breaks = seq()) you always need to know your data. Otherwise you could make mistakes with zooming to far in or out, losing sight of data and/or datapoints.

And without the dput it was not possible to check this code beforehand on your data.