Shiny App: How to get total sum by column

Question

I have two problems: -First I cannot start the table showing only zeros or blank for that reason I've created a button that set's every thing to zero which kind of works but its not ideal. -Secondly, I'm trying to calculate column sum for each column in a rhandontable but so far I havent been able to make it work.

I have been looking around for similar problems and I have found some code that looked promissing but in the end it only provided the sum for a single column or with some changes it would sum up all columns which is not what I'm after.

ui <- fluidPage(
  rHandsontableOutput('table'),
  textOutput('result'),
  actionButton("recalc", "re-enter data")
)

season<-c("Spring","Summer","Autum","Winter")

server <- function(input,output,session)({
  values <- reactiveValues(data = NULL) ## assign it with NULL

  ## button press resets now the data frame
  observeEvent(input$recalc, { 
    values$data[] <- 0
  })

  ## changes in numericInput sets all (!) new values
  observe({
    values$data <-data.frame(row.names=season,Lake=1:4,Beach=1:4, Garden=1:4,stringsAsFactors = FALSE)

  })

  observe({
    if(!is.null(input$table))
      values$data <- hot_to_r(input$table)
  })


  output$table <- renderRHandsontable({
    req(values$data)
    rhandsontable(values$data,rowHeaderWidth = 100)
  })

})

shinyApp(ui = ui, server = server)

The expected results would be a 5th column with the sum of each column. A starting table filled with zeros or blank.

If anyone could point me in the right direction it would be very much appreciated.

If you want to start your table with zeros, why don't you simply replace 1:4 with rep(0,4) in your code above? — StatsStudent, Oct 09 '19 at 01:30
@StatusStudent, thank you for the solution on the zeros it worked perfectly. Now I'm only missing the columns sums. cheers — PatraoPedro, Oct 09 '19 at 07:15

score 3 · Accepted Answer · answered Oct 09 '19 at 12:25

You can create empty cells with NA. Please check the following example to calculate colSums:

library(shiny)
library(rhandsontable)

ui <- fluidPage(
  br(),
  rHandsontableOutput('table'),
  textOutput('result'),
  br(),
  actionButton("recalc", "re-enter data")
)

rowNames <- c("Spring", "Summer", "Autum", "Winter", "Sum")
defaultDF <- data.frame(
    row.names = rowNames,
    Lake = rep(NA_integer_, 5),
    Beach = rep(NA_integer_, 5),
    Garden = rep(NA_integer_, 5),
    stringsAsFactors = FALSE
  )

server <- function(input, output, session)
  ({
    values <- reactiveValues(data = defaultDF) ## assign it with NULL

    ## button press resets now the data frame
    observeEvent(input$recalc, {
      values$data[] <- NA_integer_
    })

    observe({
      req(input$table)
        DF <- hot_to_r(input$table)
        DF[setdiff(rowNames, "Sum"),]
        DF["Sum",] <- colSums(DF[setdiff(rowNames, "Sum"),], na.rm = TRUE)
        values$data <- DF
    })

    output$table <- renderRHandsontable({
      req(values$data)
      rhandsontable(values$data, rowHeaderWidth = 100) %>%
        hot_row(nrow(values$data), readOnly = TRUE)
    })

  })

shinyApp(ui = ui, server = server)

Shiny App: How to get total sum by column

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