Dynamically adding column names in R Shiny - r

Question

Quite New to R here and not an experienced coder. I want to create a simple function to upload an external file via R shiny, but the file will not have fixed number of columns and may or may not have a column name.
In the case where the raw file does not have a header, I wish to force the name of the first column to be "Date" and the remaining columns 2,3,4...,n to be "Investment 1","Investment 2","Investment 3",...,"Investment n-1" respectively
Here's my current code, server side,
server <- function(input, output) {
rawdata <- reactive({
file_to_read = input$file
if(is.null(file_to_read)) {
return()
}
data <- read.table(file_to_read$datapath, sep = input$sep, header =
input$dataheader)
})
addcolumn <- reactive({
if(input$dataheader = FALSE) {
paste("Date",colnames(rawdata()[,1]))
for (i in 2:ncol(rawdata())) {
paste("Investment " + i, colnames(rawdata()[,i]))
}
}
})
output$datatable <- renderTable({
If(input$dataheader = FALSE) {
addcolumn(rawdata())
} else {
rawdata()
}
})
and ui side,
dashboardBody(
tabItems(
tabItem(
tabName = "import",
fluidRow(
box(
title = "Instructions",
solidHeader = TRUE,
width = 12,
status = "warning",
height = 120,
textOutput("instructionsImport")
),
box(
solidHeader = FALSE,
width = 3,
status = "primary",
fileInput("file","Choose a file to upload"),
radioButtons("sep","Separator",choices = c(Comma = ",", Space = " ",Period = ".", Tilde = "~", minus = "-")),
checkboxInput("dataheader","File has header?")
),
box(
title = "Uploaded Data",
solidHeader = TRUE,
width = 9,
status = "primary",
tableOutput("datatable")
)
)
),
Ideally, I would like the operation of adding column name to be done once after import and the resulting data table created instead of making a reactive function for adding column.
Thanks

Answer 1

Just change your server.R code to that :
server <- function(input, output) {
rawdata <- reactive({
file_to_read = input$file
if(is.null(file_to_read)) {
return()
}
data <- read.table(file_to_read$datapath, sep = input$sep, header =
input$dataheader)
if(!input$dataheader){
colnames(data)<-c("Date",paste("Investment",1:(ncol(data)-1)))
}
return(data)
})
output$datatable <- renderTable({
rawdata()
})
}