Deleting row from data.frame ( R shiny) - r

Question

I'm trying to program a shiny app which reads your *.csv file and generates a plot out of this file. The file has a header and bottom containing several lines, which the user should be able to delete within the shiny app. So basically this edited file is the source for the plot.
I'm not sure how to create the reactive part based on the input file. Tried several approaches from this page, but i can't get it to work. I attached an simplified Test.csv file.
if (!require("shiny")) install.packages("shiny", dependencies = TRUE)
if (!require("shinyjs")) install.packages("shinyjs", dependencies = TRUE)
if (!require("DT")) install.packages("DT", dependencies = TRUE)
library(shiny)
library(shinyjs)
library(DT)
ui <- fluidPage(
tabsetPanel(
tabPanel("Upload File",
titlePanel("Uploading Files"),
sidebarLayout(
sidebarPanel(
fileInput('file1', 'Choose CSV File', accept=c('text/csv', 'text/comma-separated-values,text/plain', '.csv')),
tags$br(),
checkboxInput('header', 'Header', FALSE),
radioButtons('sep', 'Separator', c(Semicolon=';', Comma=',', Tab='\t'), ','),
radioButtons('quote', 'Quote',c(None='', 'Double Quote'='"', 'Single Quote'="'"), '"'),
actionButton('delete_row', 'Delete row')
),
mainPanel(
DT::dataTableOutput('contents')
)
)
),
tabPanel("Plot",
pageWithSidebar(
headerPanel('Visualisation'),
sidebarPanel(
selectInput('xcol', 'X Variable', ""),
selectInput('ycol', 'Y Variable', "", selected = ""),
textOutput("m_out")
),
mainPanel(
plotOutput('MyPlot')
)
)
)
)
)
server <- function(input, output, session) {
data <- reactive({
req(input$file1)
inFile <- input$file1
df <- read.csv(inFile$datapath, header = input$header, sep = input$sep, quote = input$quote)
updateSelectInput(session, inputId = 'xcol', label = 'X Variable', choices = names(df), selected = names(df))
updateSelectInput(session, inputId = 'ycol', label = 'Y Variable', choices = names(df), selected = names(df)[2])
return(df)
})
### This part is the problem
###
observeEvent(input$delete_row, {
if (!is.null(input$contents_rows_selected)) {
#print(input$contents_rows_selected) #testing input
data$values <- data$values[-nrow(input$contents_rows_selected),]
}
})
###
### End of problem
output$contents = DT::renderDataTable({
data()
})
output$MyPlot <- renderPlot({
x <- data()[, c(input$xcol, input$ycol)]
plot(x)
})
}
### End of server commands
### Start Shiny App
shinyApp(ui = ui, server = server)
Thanks for your help in advance. Problem is marked with ###

Answer 1

Try making your data variable a reactiveVal(). I'd suggest also putting your input$file1 that reads-in the data frame.
In the server function:
data <- reactiveVal(NULL)
and to set its value into an event observing submitting the input file:
observeEvent(input$file1, {
df <- read.csv(inFile$datapath, header = input$header, sep = input$sep, quote = input$quote)
updateSelectInput(session, inputId = 'xcol', label = 'X Variable', choices = names(df), selected = names(df))
updateSelectInput(session, inputId = 'ycol', label = 'Y Variable', choices = names(df), selected = names(df)[2])
data(df)
})
Deleting the row then would look something like:
...
df2 <- data()
df2 <- df2[-nrow(input$contents_rows_selected),]
data(df2)
...
This will allow your other UI functions to trigger when observing changes to the (reactive) data() object.