Errors in recoding variables in shiny apps - r

Question

I'm trying to set codes to recode in shiny web application. However, it doesn't work for me.
Here's my code.
library(shiny)
library(rlang)
library(dplyr)
ui <- fluidPage(
titlePanel("Short Form Web App"),
sidebarPanel(
numericInput("num1","previous vector", value = NULL),
numericInput("num2","post vector", value = NULL),
selectInput("var","select Variable",names(mtcars)),
textInput("new_var","new variable names")
),
mainPanel(
verbatimTextOutput("tab1"),
verbatimTextOutput("tab2"),
actionButton("do","Do")
)
)
server <- function(input, output) {
output$tab1 <- renderPrint({
table(mtcars[["cyl"]])
})
rv <- reactiveValues(data = NULL)
rv$data <- mtcars
observeEvent(input$do,{
new_var <- input$new_var
new <- rv$data %>% transmute(!!new_var := case_when(input$var == input$num1 ~ input$num2))
rv$data <- bind_cols(rv$data,new)
output$tab2 <- renderPrint({
str(rv$data)
})
})
}
shinyApp(ui,server)
What I'm trying to do is recode previous vector to new vector like recode, but the result keeps showing NA..
Could anyone help me fix this problem?
I would very be very appreciated with your helps.
Thank you in advance.

Answer 1

Two issues:
As input$var is character you first have to convert to a symbol, i.e. use !!sym(input$var)
In your case_when you missed to set a default value. Hence, all values not specified to be recoded will be assigned NA.
Try this:
library(shiny)
library(rlang)
library(dplyr)
ui <- fluidPage(
titlePanel("Short Form Web App"),
sidebarPanel(
numericInput("num1","previous vector", value = NULL),
numericInput("num2","post vector", value = NULL),
selectInput("var","select Variable",names(mtcars)),
textInput("new_var","new variable names")
),
mainPanel(
verbatimTextOutput("tab1"),
verbatimTextOutput("tab2"),
actionButton("do","Do")
)
)
server <- function(input, output) {
output$tab1 <- renderPrint({
table(mtcars[["cyl"]])
})
rv <- reactiveValues(data = NULL)
rv$data <- mtcars
observeEvent(input$do,{
new_var <- input$new_var
new <- rv$data %>% transmute(!!sym(new_var) := case_when(
!!sym(input$var) == input$num1 ~ as.double(input$num2),
TRUE ~ !!sym(input$var)))
rv$data <- bind_cols(rv$data,new)
output$tab2 <- renderPrint({
str(rv$data)
})
})
}