ggplot2 Error in R: Continuous value supplied to discrete scale (2 Examples)

data(iris)                            # Loading iris as example data
iris$Petal.Width.Groups <- 1          # Modify iris data
iris$Petal.Width.Groups[iris$Petal.Width > 1 & iris$Petal.Width <= 2] <- 2
iris$Petal.Width.Groups[iris$Petal.Width > 2] <- 3
head(iris)
#   Sepal.Length Sepal.Width Petal.Length Petal.Width Species Petal.Width.Groups
# 1          5.1         3.5          1.4         0.2  setosa                  1
# 2          4.9         3.0          1.4         0.2  setosa                  1
# 3          4.7         3.2          1.3         0.2  setosa                  1
# 4          4.6         3.1          1.5         0.2  setosa                  1
# 5          5.0         3.6          1.4         0.2  setosa                  1
# 6          5.4         3.9          1.7         0.4  setosa                  1

data(iris) # Loading iris as example data iris$Petal.Width.Groups <- 1 # Modify iris data iris$Petal.Width.Groups[iris$Petal.Width > 1 & iris$Petal.Width <= 2] <- 2 iris$Petal.Width.Groups[iris$Petal.Width > 2] <- 3 head(iris) # Sepal.Length Sepal.Width Petal.Length Petal.Width Species Petal.Width.Groups # 1 5.1 3.5 1.4 0.2 setosa 1 # 2 4.9 3.0 1.4 0.2 setosa 1 # 3 4.7 3.2 1.3 0.2 setosa 1 # 4 4.6 3.1 1.5 0.2 setosa 1 # 5 5.0 3.6 1.4 0.2 setosa 1 # 6 5.4 3.9 1.7 0.4 setosa 1

install.packages("ggplot2")           # Install ggplot2 package
library("ggplot2")                    # Load ggplot2

install.packages("ggplot2") # Install ggplot2 package library("ggplot2") # Load ggplot2

ggplot(iris, aes(x = Petal.Length,    # Adding colors leads to error
                 group = Petal.Width.Groups,
                 color = Petal.Width.Groups)) +
  geom_boxplot() + 
  scale_color_manual(values = c("red", "green", "blue"))
# Error: Continuous value supplied to discrete scale

ggplot(iris, aes(x = Petal.Length, # Adding colors leads to error group = Petal.Width.Groups, color = Petal.Width.Groups)) + geom_boxplot() + scale_color_manual(values = c("red", "green", "blue")) # Error: Continuous value supplied to discrete scale

ggplot(iris, aes(x = Petal.Length,    # Applying factor function
                 group = Petal.Width.Groups,
                 color = factor(Petal.Width.Groups))) +
  geom_boxplot() + 
  scale_color_manual(values = c("red", "green", "blue"))

ggplot(iris, aes(x = Petal.Length, # Applying factor function group = Petal.Width.Groups, color = factor(Petal.Width.Groups))) + geom_boxplot() + scale_color_manual(values = c("red", "green", "blue"))