R multiple choice questionnaire data to ggplot

Question

I have a Qualtrics multiple choice question that I want to use to create graphs in R. My data is organized so that you can answer multiple answers for each question. For example, participant 1 selected multiple choice answers 1 (Q1_1) & 3 (Q1_3). I want to collapse all answer choices in one bar graph, one bar for each multiple response option (Q1_1:Q1_3) divided by the number of respondents who answered this question (in this case, 3).

df <- structure(list(Participant = 1:3, A = c("a", "a", ""), B = c("", "b", "b"), C = c("c", "c", "c")), .Names = c("Participant", "Q1_1", "Q1_2", "Q1_3"), row.names = c(NA, -3L), class = "data.frame")

I want to use ggplot2 and maybe some sort of loop through Q1_1: Q1_3?

Answer 1

Perhaps this is what you want

f <- 
  structure(
    list(
      Participant = 1:3,
      A = c("a", "a", ""),
      B = c("", "b", "b"),
      C = c("c", "c", "c")),
    .Names = c("Participant", "Q1_1", "Q1_2", "Q1_3"),
    row.names = c(NA, -3L),
    class = "data.frame"
  )


library(tidyr)
library(dplyr)
library(ggplot2)

nparticipant <- nrow(f)
f %>% 
  ## Reformat the data
  gather(question, response, starts_with("Q")) %>%
  filter(response != "") %>%

  ## calculate the height of the bars
  group_by(question) %>%
  summarise(score = length(response)/nparticipant) %>%

  ## Plot
  ggplot(aes(x=question, y=score)) +
  geom_bar(stat = "identity")