Shiny renderUI with multiple inputs - r

Question

My Shiny App has multiple inputs that depend on the number of variables used. A simplified version, though not working, is below. I was able to get the UI to update based upon the numericInput using a function called Make.UI which I used to make uiOutput, but getting the inputs back into the server is beyond my Shiny skill set! Any suggestions would be greatly appreciated.
gwynn
library(shiny)
D = matrix(runif(400), nrow = 20)
colnames(D) = labs = sapply(1:20, function(i) {paste0("col",i)})
# Define UI for application that summarises data
ui <- fluidPage(
# Application title
titlePanel("Summaries"),
# Select columns to get fed into summary
tabsetPanel(
tabPanel("Matching Variables Info",
sidebarPanel(
numericInput("NoVars","No. of variables to summarize",
value = 3, min = 2, max = dim(D)[2]),
uiOutput("VarsInput")
),
# Show summaries of columns choosen above
mainPanel(
verbatimTextOutput("dataInfo")
)
)
)
)
# Define the server code
server <- function(input, output){
Make.UI <- function(NoV){
C = sapply(1:NoV, function(i){paste0("cols",i)})
L = sapply(1:NoV, function(i){paste0("label",i)})
output = tagList()
for(i in seq_along(1:NoV)){
output[[i]] = tagList()
output[[i]][[1]] = selectInput(C[i], "Variable to summarize:", labs)
output[[i]][[2]] = textInput(L[i], label = "Label for variable:",
value = "Label for variable Here")
} ## for loop
output
} # closes Make.UI function
K <- reactive({
input$NoVars
})
output$VarsInput <- renderUI({
Make.UI(K())
})
output$dataInfo <- renderPrint({
C <- sapply(1:K(), function(i) {input[[paste0("cols",i)]]})
## the code in the line above doesn't work
summary(D[, C()])
})
}
# Return a Shiny app object
shinyApp(ui = ui, server = server)

Answer 1

Like I wrote in the first comment, I am unsure about the Make.UI()function. If you really want to keep it as a seperate function you should make it reactive. Or just use it as I did in the code below.
Moreover, in output$dataInfo <- renderPrint({ C is not a reactive() function so you would need to remove brackets there.
library(shiny)
D = matrix(runif(400), nrow = 20)
colnames(D) = labs = sapply(1:20, function(i) {paste0("col",i)})
# Define UI for application that summarises data
ui <- fluidPage(
# Application title
titlePanel("Summaries"),
# Select columns to get fed into summary
tabsetPanel(
tabPanel("Matching Variables Info",
sidebarPanel(
numericInput("NoVars","No. of variables to summarize",
value = 3, min = 2, max = dim(D)[2]),
uiOutput("VarsInput")
),
# Show summaries of columns choosen above
mainPanel(
verbatimTextOutput("dataInfo")
)
)
)
)
# Define the server code
server <- function(input, output){
K <- reactive({
input$NoVars
})
output$VarsInput <- renderUI({
NoV = K()
C = sapply(1:NoV, function(i){paste0("cols",i)})
L = sapply(1:NoV, function(i){paste0("label",i)})
output = tagList()
for(i in seq_along(1:NoV)){
output[[i]] = tagList()
output[[i]][[1]] = selectInput(C[i], "Variable to summarize:", labs)
output[[i]][[2]] = textInput(L[i], label = "Label for variable:",
value = "Label for variable Here")
}
output
})
output$dataInfo <- renderPrint({
C <- sapply(1:K(), function(i) {input[[paste0("cols",i)]]})
## the code in the line above doesn't work
summary(D[, C])
})
}
# Return a Shiny app object
shinyApp(ui = ui, server = server)