geom_ribbon: create a rule for colour changes using fill

Question

I'd like in my pred_avg dataset to create a rule (pred_avg$canopycoverSDmin < pred_avg$covermin) for color changes using fill in geom_ribbon using ggplot2, but despite my variable pred_avg$groups in fill = groups is a factor doesn't work and I have always Error: Aesthetics can not vary with a ribbon as output.

In my example:

library(ggplot2)

#Open data set
pred_avg<- read.csv("https://raw.githubusercontent.com/Leprechault/trash/main/cc_mean_CI.csv")
str(pred_avg)
#'data.frame':  40323 obs. of  9 variables:
# $ X               : int  1 2 3 4 5 6 7 8 9 10 ...
# $ DATE            : chr  "2021-06-04" "2021-06-04" "2021-06-04" "2021-06-04" ...
# $ canopycover     : num  47 47 47 47 47 ...
# $ se.cc           : num  1.6 1.57 1.54 1.54 1.54 ...
# $ n.cc            : int  3073 3073 3073 3073 3073 3073 3073 3073 3073 3073 ...
# $ canopycoverSDmax: num  50.2 50.1 50 50 50 ...
# $ canopycoverSDmin: num  43.9 44 44 44 44 ...
# $ covermin        : num  43.1 43.1 43.1 43.1 43.1 ...
# $ covermax        : num  85.2 85.2 85.2 85.2 85.2 ...

# Create the variable (`groups`) for colours changes
pred_avg$groups <- ifelse(pred_avg$canopycoverSDmin < pred_avg$covermin, "A", "H") 
pred_avg$groups <-as.factor(pred_avg$groups)

# Create the plot
         ggplot(pred_avg, aes(x = DATE, y = canopycover, group = 1), fill=factor(groups)) +
         geom_point () +
         geom_line() + 
         geom_ribbon(data=pred_avg, aes(ymin = canopycoverSDmin, ymax = canopycoverSDmax, fill = groups), alpha = 0.1) +
         scale_fill_manual(values=c("red", "green"), name="fill") +
         geom_ribbon(aes(ymin = covermin, ymax = covermax), alpha = 0.1) +
         scale_x_date(breaks = "1 week") + 
           theme_bw() + theme(panel.border = element_blank(), panel.grid.major = element_blank(),
                              axis.text=element_text(size=10),
                              axis.title=element_text(size=12),
                              plot.title = element_text(size = 14, face = "bold"),
                              legend.title = element_blank(),
                              axis.text.x = element_text(angle = 90, hjust = 1),
                              panel.grid.minor = element_blank(), axis.line = element_line(colour = "black"))

Error: Aesthetics can not vary with a ribbon
Run `rlang::last_error()` to see where the error occurred.

Please, any help with it?

Answer 1

When you specify something in the original ggplot() it will be inherited by subsequent layers. Don't put group = 1 up there globally. If you need it for the line layer, put group = 1 just in geom_line. Similarly, don't put fill=factor(groups) in the base ggplot() call because you don't want it being used in the point layer, the second ribbon layer, etc. You only need it in the first ribbon layer, so only put it there. (And you need to put it inside aes() since it references a column name!)

pred_avg$DATE = as.Date(pred_avg$DATE)

# Create the plot
ggplot(pred_avg, aes(x = DATE, y = canopycover)) +
  geom_point () +
  geom_line(group = 1) +
  geom_ribbon(
    data = pred_avg,
    aes(
      ymin = canopycoverSDmin, 
      ymax = canopycoverSDmax, 
      fill = groups),
    alpha = 0.1
  ) +
  scale_fill_manual(values = c("red", "green"), name = "fill") +
  geom_ribbon(aes(ymin = covermin, ymax = covermax), alpha = 0.1) +
  scale_x_date(breaks = "1 week") +
  theme_bw() + theme(
    panel.border = element_blank(),
    panel.grid.major = element_blank(),
    axis.text = element_text(size = 10),
    axis.title = element_text(size = 12),
    plot.title = element_text(size = 14, face = "bold"),
    legend.title = element_blank(),
    axis.text.x = element_text(angle = 90, hjust = 1),
    panel.grid.minor = element_blank(),
    axis.line = element_line(colour = "black")
  )