R Shiny: Perform a series of functions on reactive input - r

Question

I want to perform a series of tasks on a data.frame that will be loaded by the user via actionButton. Here is an example where I want to remove rows with NAs in the third column of the data.frame selected by the user. I get the error:
"Warning: Error in observeEventHandler: object 'df' not found
Stack trace (innermost first):
65: observeEventHandler [(file location).R#56]"
Why doesn't observeEvent recognize the variable f?
Server.R
library(shiny)
shinyServer <- function(input, output) {
filedata <- reactive({
infile <- input$Samples
if (is.null(infile)) {
# User has not uploaded a file yet
return(NULL)
}
df <- read.table(infile$datapath,sep="\t",skip =0, header = TRUE,na.strings = "NA",stringsAsFactors=FALSE)
})
observeEvent(input$Click, {
selectA <- df[complete.cases(f[,3]),]
}
}
ui.R
library(shiny)
shinyUI( <- fluidPage(
tabPanel("Inputs",
wellPanel(fileInput(inputId = "Samples", label = "Import File"),
actionButton(inputId = "Click", label = "Samples")),
h2('Results'),
dataTableOutput("Results")))

Answer 1

Maybe I didn't do a good job of articulating my question. Here is the answer that I was looking for.
Server.R
library(shiny)
shinyServer <- function(input, output) {
filedata <- reactive({
infile <- input$Samples
if (is.null(infile)) {
# User has not uploaded a file yet
return(NULL)
}
read.table(infile$datapath,sep="\t",skip =0, header = TRUE,na.strings = "NA",stringsAsFactors=FALSE)
})
observeEvent(input$Click, {
df <- filedata()
selectA <- df[complete.cases(df[,3]),]
}
}