Add extra cells with each entry to table output - r

Question

I am trying to make an xlsx sheet of customers orders of certain items. I created a shiny app to input each order in the form of a datatable row which is added to the table on click of "Add" Button. But I face a problem, each time I add a new order (row) an extra cell of row number is generated in all the previous ones like in the picture.
and all row cells are shifted to the right!!
This is my code:
library(shiny)
library(shinythemes)
library(readxl)
library(xlsx)
library(DT)
items <- read_excel("items.xlsx",col_names = F)
colnames(items) <- c("Items", "Euro", "Cost")
ui <- fluidPage(theme = shinytheme('journal'),
sidebarLayout(
sidebarPanel(
tags$img(height = 118, width = 160, src="logo.jpg"),
br(),br(),
textInput('name','Name'),
br(),
selectizeInput(inputId = "item",
label = "Item",
choices = c(items$Items),
options = list(
placeholder = '',
onInitialize = I('function() { this.setValue(""); }'))),
br(),
numericInput('number','Quantity',value = 1,step = 1),
br(),
numericInput('price','Price/pc',value = ''),
br(),
actionButton(inputId = "button", label = "Add", icon = icon("plus"),
style="color: #fff; background-color: #337ab7; border-color: #2e6da4"),
width = 3),
mainPanel(DTOutput('out')))
)
server <- function(input, output,session) {
observeEvent(input$button,{
order <- data.frame(read_excel("Order.xlsx"))
price <- items[items$Items == input$item,][c(2,3)]
order[nrow(order) + 1,] <- c(ifelse(input$name %in% order$Name,'',input$name),input$item,input$number,
price,price[2]* input$number,input$price*input$number,
(input$price*input$number) - (price[2]* input$number))
write.xlsx(order,'order.xlsx')
output$out<- renderDT({datatable(order)})
})
}
shinyApp(ui = ui, server = server)
items.xlsx
Items Euro Cost
some item 2.5 10
some item2 5 20
some item3 4 18
order.xlsx
Name Item Quantity Euro Cost Total cost Total price Gain
can somebody know what is the cause for that and how to solve?
Thanks all

Answer 1

I couldn't recreate your exact app because I had trouble getting xlsx package to load on my system. I recreated a similar working example by saving the two excel files as CSV files and using readr read_csv and write_csv in place of your read_excel and write.xlsx. This version appears to work as you want it to but with csv output instead of excel. Having a read of the xlsx documentation I might have a guess that row names are being written out each time you write.xlsx and this is showing up when you read them back in. Could it be that you need to pass row.names = FALSE to your write.xlsx call?
https://cran.r-project.org/web/packages/xlsx/xlsx.pdf
library(shiny)
library(shinythemes)
library(DT)
library(readr)
items <- readr::read_csv("items.csv",col_names = T)
ui <- fluidPage(theme = shinytheme('journal'),
sidebarLayout(
sidebarPanel(
tags$img(height = 118, width = 160, src="logo.jpg"),
br(),br(),
textInput('name','Name'),
br(),
selectizeInput(inputId = "item",
label = "Item",
choices = c(items$Items),
options = list(
placeholder = '',
onInitialize = I('function() { this.setValue(""); }'))),
br(),
numericInput('number','Quantity',value = 1,step = 1),
br(),
numericInput('price','Price/pc',value = ''),
br(),
actionButton(inputId = "button", label = "Add", icon = icon("plus"),
style="color: #fff; background-color: #337ab7; border-color: #2e6da4"),
width = 3),
mainPanel(DTOutput('out')))
)
server <- function(input, output,session) {
observeEvent(input$button,{
order <- data.frame(read_csv("order.csv"))
price <- items[items$Items == input$item,][c(2,3)]
order[nrow(order) + 1,] <- c(ifelse(input$name %in% order$Name,'',input$name),input$item,input$number,
price,price[2]* input$number,input$price*input$number,
(input$price*input$number) - (price[2]* input$number))
write_csv(order,'order.csv')
output$out<- renderDT({datatable(order)})
})
}
shinyApp(ui = ui, server = server)

Answer 2

Try to perform data reading and data wrangling outside of the observer as shown below.
items <- read.table(text='"Items","Euro","Cost"
some item, 2.5, 10
some item2, 5,20
some item3, 4,18', header=TRUE, sep=",")
ui <- fluidPage(theme = shinytheme('journal'),
sidebarLayout(
sidebarPanel(
tags$img(height = 118, width = 160, src="logo.jpg"),
br(),br(),
textInput('name','Name'),
br(),
selectizeInput(inputId = "item",
label = "Item",
choices = c(items$Items),
options = list(
placeholder = '',
onInitialize = I('function() { this.setValue(""); }'))),
br(),
numericInput('number','Quantity',value = 1,step = 1),
br(),
numericInput('price','Price/pc',value = ''),
br(),
actionButton(inputId = "button", label = "Add", icon = icon("plus"),
style="color: #fff; background-color: #337ab7; border-color: #2e6da4"),
width = 3),
mainPanel(DTOutput('out')))
)
server <- function(input, output,session) {
order <- eventReactive(input$button,{
req(input$number,input$price,input$name)
order <- data.frame(read_excel("order.xlsx"))
price <- items[items$Items == input$item,][c(2,3)]
order[nrow(order) + 1,] <- c(ifelse(input$name %in% order$Name,'',input$name),input$item,input$number,
price,price[2]* input$number,input$price*input$number,
(input$price*input$number) - (price[2]* input$number))
order
})
observeEvent(input$button,{ write.xlsx(order(),'order.xlsx') })
output$out<- renderDT({datatable(order())})
}
shinyApp(ui = ui, server = server)