How to use a reactive function to create a DF in R Shiny

Question

I am trying to create a wordcloud shiny app after going through a DataCamp course. In the course they use a custom create_wordcloud() function to make the app. If someone has the code for it, it would make my life easier.

Anyways, I am trying to go about my own way since I don't have the custom function and will be using wordcloud2() function.

I am having trouble with using reactive functions to make the Shiny app. Essentially I am trying to make it so that the user can select the number of words and change the background in the wordcloud using the UI. For this to happen, I need to convert the text provided by the user a dataframe, order the df by word count, and then subset the df into what ever number the user selects in the app UI.

Here is my code:

library(shiny)
library(colourpicker)
library(tidyverse)


ui <- fluidPage(
  h1("Word Cloud"),
  sidebarLayout(
    sidebarPanel(
      # Add a textarea input
      textAreaInput("text", "Enter text", rows = 7),
      numericInput("num", "Maximum number of words", 25),
      colourInput("col", "Background color", value = "white")
    ),
    mainPanel(
      wordcloud2Output("cloud")
    )
  )
)

server <- function(input, output) {
  df_data <- reactive({
    input$text %>% 
      term_stats(., drop_punct = TRUE, drop = stopwords_en) %>% 
      order_by(desc(count))
  })
  
  output$cloud <- renderWordcloud2({
    # Use the textarea's value as the word cloud data source
    wordcloud2(data = df_data()[1:input$num, ],
                     backgroundColor = input$col)
  })
}

shinyApp(ui = ui, server = server)

The error that I get is:

Warning: Error in : Input must be a vector, not a function.

I really look forward to hearing answers from the community and improve my reactive programming skills!

Thank you!

Answer 1

Solution 1: Obtaining actual code create_wordcloud function as follows:

create_wordcloud <- function(data, num_words = 100, background = "white") {
  
  # If text is provided, convert it to a dataframe of word frequencies
  if (is.character(data)) {
    corpus <- Corpus(VectorSource(data))
    corpus <- tm_map(corpus, tolower)
    corpus <- tm_map(corpus, removePunctuation)
    corpus <- tm_map(corpus, removeNumbers)
    corpus <- tm_map(corpus, removeWords, stopwords("english"))
    tdm <- as.matrix(TermDocumentMatrix(corpus))
    data <- sort(rowSums(tdm), decreasing = TRUE)
    data <- data.frame(word = names(data), freq = as.numeric(data))
  }
  
  # Make sure a proper num_words is provided
  if (!is.numeric(num_words) || num_words < 3) {
    num_words <- 3
  }  
  
  # Grab the top n most common words
  data <- head(data, n = num_words)
  if (nrow(data) == 0) {
    return(NULL)
  }
  
  wordcloud2(data, backgroundColor = background)
}

Solution 2: Provided by @Xiang in the comments section:

ui <- fluidPage(
  h1("Word Cloud"),
  sidebarLayout(
    sidebarPanel(
      # Add a textarea input
      textAreaInput("text", "Enter text", rows = 7),
      numericInput("num", "Maximum number of words", 25),
      colourInput("col", "Background color", value = "white")
    ),
    mainPanel(
      wordcloud2Output("cloud")
    )
  )
)

server <- function(input, output) {
  df_data <- reactive({
    input$text %>% 
      term_stats(., drop_punct = TRUE, drop = stopwords_en) %>% 
      arrange(desc(count))
  })
  
  output$cloud <- renderWordcloud2({
    # Use the textarea's value as the word cloud data source
    wordcloud2(data = df_data()[1:input$num, ],
                     backgroundColor = input$col)
  })
}

shinyApp(ui = ui, server = server)