Want to plot dual-y-axis and show the legend in ggplot2

Question

I want to plot a dual-y-axis in ggplot. The primary y-axis is called Payout (GDD) in my dataset, while the secondary y-axis is called yield_loss_ratio_1 in my dataset. I have an issue in the secondary yield_loss_ratio_1 y-axis where the its counts are similar to the counts of the primary y-axis and not representing actual counts that I want in the secondary axis.

Any ideas and thoughts on how to plot the chart as I require and to show the legend of the plot?

I need to plot some thing similar to the below image.

And this is the image I got from the ggplot:

I tried this chunk of code:

fig_GDD <- payout_yeild_loss %>%
  ggplot() +
  geom_col(aes(x = year, y = `Payout (GDD)`), fill = "black") +
  geom_point(aes(x = year, y = yield_loss_ratio_1),
    color = "red",
    size = 3,
    shape = 15
  ) +
  geom_line(aes(x = year, y = yield_loss_ratio_1),
    color = "red",
    size = 1
  ) +
  scale_y_continuous(
    name = "Payout (RM/°C)",
    sec.axis = sec_axis(~.,
      name = "Yield loss ratio (%)"
    ),
    expand = c(0.01, 0)
  ) +
  scale_x_date(
    date_breaks = "2 year",
    date_labels = "%Y",
    expand = c(0.01, 0)
  ) +
  labs(
    x = " "
  ) +
  theme_classic()

Here is the dput of my data

structure(list(year = structure(c(11323, 11688, 12053, 12418, 
12784, 13149, 13514, 13879, 14245, 14610, 14975, 15340, 15706, 
16071, 16436, 16801), class = "Date"), `seaon 1 (kg/ha)` = c(5215, 
5585, 5690, 5730, 6084, 5982, 5849, 5971, 6189, 6070, 6049, 6312, 
6595, 6478, 6282, 6247), `Season 2 (kg/ha)` = c(4845, 5259, 5220, 
5440, 3936, 5463, 5429, 6120, 5656, 5890, 5147, 5266, 6452, 5161, 
6141, 5344), `Cumulative GDD - S1 (C°)` = c(544, 557, 552, 549, 
568, 547, 557, 549, 580, 567, 562, 565, 557, 576, 564, 563), 
    `Cumulative rainfall - S2 (mm)` = c(81, 96, 26, 71, 490, 
    48, 163, 36, 17, 104, 76, 67, 23, 242, 87, 120), `Payout (GDD)` = c(70, 
    12, 34, 48, 0, 56, 13, 47, 0, 0, 0, 0, 11, 0, 0, 0), `Payout(CR)` = c(0, 
    0, 0, 0, 242, 0, 214, 0, 0, 0, 0, 0, 0, 242, 0, 42), yield_loss_ratio_1 = c(15, 
    8, 6, 5, 0, 1, 3, 1, 0, 0, 0, 0, 0, 0, 0, 0), yeild_loss_ratio_2 = c(12, 
    3, 4, 0, 38, 0, 0, 0, 0, 0, 5, 3, 0, 5, 0, 1)), row.names = c(NA, 
-16L), class = c("tbl_df", "tbl", "data.frame"))

user_12993861 · Answer

The issue with your legend is that you have set the colors as arguments. If you want to have a legend you have to map on aesthetics and set your color via scale_xxx_manaual. The issue with the scale of your secondary axis is that YOU have to do the rescaling of the axis and the data manually. ggplot2 will not do that for your. In the code below I use scales::rescale to first rescale the data to be displayed on the secondary axis and to retransform inside sec_axis():

library(ggplot2)

range_yield <- range(payout_yeild_loss$yield_loss_ratio_1)
range_gdd <- range(payout_yeild_loss$`Payout (GDD)`)

payout_yeild_loss$yield_loss_ratio_1 <- scales::rescale(payout_yeild_loss$yield_loss_ratio_1, to = range_gdd)
ggplot(payout_yeild_loss) +
  geom_col(aes(x = year, y = `Payout (GDD)`, fill = "black")) +
  geom_point(aes(x = year, y = yield_loss_ratio_1,  color = "red"),
    size = 3,
    shape = 15
  ) +
  geom_line(aes(x = year, y = yield_loss_ratio_1, color = "red"),
    size = 1
  ) +
  scale_y_continuous(
    name = "Payout (RM/°C)",
    sec.axis = sec_axis(~ scales::rescale(., to = range_yield),
      name = "Yield loss ratio (%)"
    ),
    expand = c(0.01, 0)
  ) +
  scale_x_date(
    date_breaks = "2 year",
    date_labels = "%Y",
    expand = c(0.01, 0)
  ) +
  scale_fill_manual(values = "black") +
  scale_color_manual(values = "red") +
  labs(
    x = " "
  ) +
  theme_classic()

Want to plot dual-y-axis and show the legend in ggplot2

1 Answers