Data manipulation on a reactive event - shiny

Question

I am creating a data frame, that is dynamically created when the user inputs a search term, in order to do this i have an action button, and the data frame is created when the "go" button is pressed.
Once this is done i need to perform various data manipulations on the DF, and out put different graphs.
i am struggling to understand how i do the data manipulation in Shiny, i have some simplified example code below:
library(shiny)
library(sp)
library(stringr)
library(tidyr)
library(tidyverse)
library(tm)
library(ggplot2)
library(stringi)
library(plyr)
library(dplyr)
ui <- fluidPage(
fluidRow(
column( 4, titlePanel("Twitter Analytics")),
column( 3),
column( 4,
textInput("searchstring",
label = "",
value = "")),
column(1,
br(),
actionButton("action", "go"))
),
fluidRow(
column( 12, tabsetPanel(
tabPanel("one",
fluidRow(
column(3 ),
column(9, plotOutput("ttext"))
)
),
tabPanel("two"),
tabPanel("three")
)
)
)
)
server <- function(input, output) {
tweet <- eventReactive(input$action,{
num <- c(1,2,3,4,50)
text <- c("this is love love something", "this is not hate hate hate something", "#something islove rethched this not", " Shiny is love confusing me", "this is hate also somthing difficult")
letter<- c("a", "b", "c", "D", "e")
tweetdf <- data.frame(num, text, letter)
})
tdm <- if( is.null(tweetdf) ){return()}
else{
tweetdf$text <- tolower(tweetdf$text)
# tweetdf #UserName
tweetdf$text <- gsub("#\\w+", "", tweetdf$text)
#remove punctuation
tweetdf$text <- gsub("[[:punct:]]", "", tweetdf$text)
#remove links
tweetdf$text <- gsub("http\\w+", "", tweetdf$text)
# Remove tabs
tweetdf$text <- gsub("[ |\t]{2,}", "", tweetdf$text)
# Remove blank spaces at the beginning
tweetdf$text <- gsub("^ ", "", tweetdf$text)
# Remove blank spaces at the end
corpus <- iconv(tweetdf$text, to = "ASCII")
corpus <- Corpus(VectorSource(corpus))
corpus <- tm_map(corpus, removePunctuation)
corpus <- tm_map(corpus, removeNumbers)
cleanset <- tm_map(corpus, removeWords, stopwords('english'))
tdm <- TermDocumentMatrix(cleanset)
tdm <- as.matrix(tdm)
w <- rowSums(tdm)
}
output$ttext <- renderPlot({
library(RColorBrewer)
barplot(w)
})
output$wordCl <- renderPlot({
library(wordcloud2)
w <- data.frame(names(w), w)
colnames(w) <- c('word', 'freq')
wordcloud2(w,
color = 'random-dark',
size = 0.7,
shape = 'circle',
rotateRatio = 0.5,
minSize = 1)
})
}
shinyApp(ui, server)
i keep getting the error message that tweetdf does not exist, This should not exist, until the user has entered a search term and clicked "go"
What is the best way to approach this problem, is this even the right spot to do this

Answer 1

It tells you that tweetdf doest not exist because the result of eventReactive (tweetdf) is assign to the variable tweet, which makes tweet your actual reactive variable with the result of tweetdf in.
Also the problem in your code is that you mix classic variables with reactive variables.
You can access reactive variables by adding parenthesis at the end of the variable()
Here is a working example:
library(shiny)
library(sp)
library(stringr)
library(tidyr)
library(tidyverse)
library(tm)
library(ggplot2)
library(stringi)
library(plyr)
library(dplyr)
library(RColorBrewer)
library(wordcloud2)
ui <- fluidPage(
fluidRow(
column( 4, titlePanel("Twitter Analytics")),
column( 3),
column( 4,
textInput("searchstring",
label = "",
value = "")),
column(1,
br(),
actionButton("action", "go"))
),
fluidRow(
column( 12, tabsetPanel(
tabPanel("one",
fluidRow(
column(3 ),
column(9, plotOutput("ttext"))
)
# ,fluidRow(wordcloud2Output("wordCl"))
),
tabPanel("two"),
tabPanel("three")
)
)
)
)
server <- function(input, output) {
w <- eventReactive(input$action,{
num <- c(1,2,3,4,50)
text <- c("this is love love something", "this is not hate hate hate something", "#something islove rethched this not", " Shiny is love confusing me", "this is hate also somthing difficult")
letter<- c("a", "b", "c", "D", "e")
tweetdf <- data.frame(num, text, letter)
tdm <- if( is.null(tweetdf) ){return()} ## should not use return here as this is not a function
else{
print(tweetdf)
tweetdf$text <- tolower(tweetdf$text)
# tweetdf #UserName
tweetdf$text <- gsub("#\\w+", "", tweetdf$text)
#remove punctuation
tweetdf$text <- gsub("[[:punct:]]", "", tweetdf$text)
#remove links
tweetdf$text <- gsub("http\\w+", "", tweetdf$text)
# Remove tabs
tweetdf$text <- gsub("[ |\t]{2,}", "", tweetdf$text)
# Remove blank spaces at the beginning
tweetdf$text <- gsub("^ ", "", tweetdf$text)
# Remove blank spaces at the end
corpus <- iconv(tweetdf$text, to = "ASCII")
corpus <- Corpus(VectorSource(corpus))
corpus <- tm_map(corpus, removePunctuation)
corpus <- tm_map(corpus, removeNumbers)
cleanset <- tm_map(corpus, removeWords, stopwords('english'))
tdm <- TermDocumentMatrix(cleanset)
tdm <- as.matrix(tdm)
w <- rowSums(tdm)
}
})
output$ttext <- renderPlot({
barplot(w())
})
output$wordCl <- renderWordcloud2({
w <- data.frame(names(w()), w())
colnames(w) <- c('word', 'freq')
wordcloud2(w,
color = 'random-dark',
size = 0.7,
shape = 'circle',
rotateRatio = 0.5,
minSize = 1)
})
}
shinyApp(ui, server)