CODEWITHSUNDEEP
rggplot2
BLuta
BLuta

Reputation: 247

Add values to legend that don't exist in dataset

I am trying to have A, B, C, D AND E in the legend of my geom_bar chart, even if those values do not exist in my dataset. Is there a way to do that in R? Below is the code I currently have...

classes_filtered <- classes %>% filter(teacher == "Mrs. Smith") %>% summarize(total_students = sum(grades))

possible_grades <- c("A", "B", "C", "D", "E", "NA")

#grades$type <- factor(grades$type, levels = c("A", "B", "C", "D", "E", "NA"))

ggplot(classes_filtered, aes(x = subject, y = total_students, fill = Grades_Given)) + 
  geom_bar(stat = "identity", colour = "black") + 
#  scale_color_manual(values = c("A", "B", "C", "D", "E", "NA"), drop = FALSE) +
  labs(x="Subject", y="Number of Students", fill = "Grade") +
  ggtitle("Grades Given per Subject")

Along with the dataset I'm working with. Any assistance is truly appreciated. Thanks.

classes_filtered  <- read.csv(text="
teacher, subject, Grades_Given, total_students
Mrs. Smith, English, NA, 1
Mrs. Smith, Algebra, C, 2
Mrs. Smith, Algebra, D, 1
Mrs. Smith, Geometry, C, 8
Mrs. Smith, Geometry, D, 7
Mrs. Smith, Biology, C, 6
Mrs. Smith, Biology, D, 7
Mrs. Smith, Biology, NA, 3
Mrs. Smith, Chemistry, C, 1
Mrs. Smith, Chemistry, D, 4
Mrs. Smith, Chemistry, NA, 2
Mrs. Smith, Literature, C, 7
Mrs. Smith, Literature, D, 4
Mrs. Smith, Literature, NA, 2
Mrs. Smith, Spanish, B, 2
Mrs. Smith, Spanish, C, 1
Mrs. Smith, French, D, 1
Mrs. Smith, Latin, C, 4
Mrs. Smith, Latin, D, 6
Mrs. Smith, Latin, NA, 2
Mrs. Smith, SAT Prep, A, 1
Mrs. Smith, SAT Prep, C, 4
Mrs. Smith, SAT Prep, D, 2
Mrs. Smith, SAT Prep, NA, 1
Mrs. Smith, NA, C, 7
Mrs. Smith, NA, D, 6
Mrs. Smith, NA, NA, 1", strip.white=TRUE)

Upvotes: 2

Views: 204

Answers (1)

MrFlick
MrFlick

Reputation: 206242

You can use scale_fill_discrete (not scale_color_discrete since you used fill= and not color= in the aes()) with specific limits= and drop= values.

ggplot(classes_filtered, aes(x = subject, y = total_students, fill = Grades_Given)) + 
  geom_bar(stat = "identity", colour = "black") + 
  scale_fill_discrete(limits = possible_grades, drop = FALSE) +
  labs(x="Subject", y="Number of Students", fill = "Grade") +
  ggtitle("Grades Given per Subject")

Upvotes: 4

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