R shiny datatable with numericinput and reactive c

Question

I am building a shiny datatable with one column for numericinput and the other reactive to the input. It is similar to what you can do in excel with equation embedded in cells. I am giving iris as example below and trying to calculate petal area. So peal area equals Petal.Length*Petal.Width/Adjust. The adjust parameter will be typed in by user to adjust area. A similar question was asked here but with no direct answer. Insert a numeric input for each row - R Shiny

library(shiny)
library(DT)
library(dplyr)

ui <- basicPage(

  DT::dataTableOutput('x1')
)

server <- function(input, output, session) { 
  # create a character vector of shiny inputs 
  shinyInput = function(FUN, len, id, ...) { 
    inputs = character(len) 
    for (i in seq_len(len)) { 
      inputs[i] = as.character(FUN(paste0(id, i), label = NULL, ...))
    } 
    inputs 
  } 

  # obtain the values of inputs 
  shinyValue = function(id, len) { 
    unlist(lapply(seq_len(len), function(i) { 
      value = input[[paste0(id, i)]] 
      if (is.null(value)) 1 else value 
    })) 
  } 

  # a sample data frame 
  DF <- reactive(
    iris <- iris %>%
      mutate(
        adjust = shinyInput(numericInput, nrow(iris), 'adj', value = 1),
        Petal_Area = Petal.Length*Petal.Width/shinyValue('adj', nrow(iris)) 
      )
  )

  # render the table containing shiny inputs 
  output$x1 = DT::renderDataTable(

    # use slider to control number of rows shown in table
    DF(), server = FALSE, escape = FALSE, options = list( 
      preDrawCallback = JS('function() { 
                           Shiny.unbindAll(this.api().table().node()); }'), 
      drawCallback = JS('function() { 
                        Shiny.bindAll(this.api().table().node()); } ') 
      ) 
      ) 
} 

shinyApp(ui, server)

Answer 1

This is an incomplete answer. In the hope that another user may be able to improve upon it. If not then this is the best possible answer.

I tried now for about half an hour but for some reason (maybe cause DT is not meant to be used like Excel), I can't get the result of the calculation in the DT-table. However reactivity and calculation work if I do not display the result in the DT-table!

I only made two changes:

1. I added a debugging table
2. I replaced your dplyr-code and removed the calculation

The code looks like this:

library(shiny)
library(DT)

ui <- basicPage(
  DT::dataTableOutput('x1'),
  tableOutput('debug')
)

server <- function(input, output, session) { 
  # create a character vector of shiny inputs 
  shinyInput = function(FUN, len, id, ...) { 
    inputs = character(len) 
    for (i in seq_len(len)) { 
      inputs[i] = as.character(FUN(paste0(id, i), label = NULL, ...))
    } 
    inputs 
  } 

  # obtain the values of inputs 
  shinyValue = function(id, len) { 
    unlist(lapply(seq_len(len), function(i) { 
      value = input[[paste0(id, i)]] 
      if (is.null(value)) 1 else value 
    })) 
  } 

  # a sample data frame 
  DF <- reactive({
    iris_adj <- iris
    iris_adj$adjust<-shinyInput(numericInput, nrow(iris), 'adj', value = 1)
    # iris_adj$Petal_area<-iris$Petal.Length*iris$Petal.Width/shinyValue('adj',nrow(iris))
    return(iris_adj)
  })


  # render the table containing shiny inputs 
  output$x1 <- DT::renderDataTable(

    # use slider to control number of rows shown in table
    DF(), server = FALSE, escape = FALSE, options = list( 
      preDrawCallback = JS('function() { 
                           Shiny.unbindAll(this.api().table().node()); }'), 
      drawCallback = JS('function() { 
                        Shiny.bindAll(this.api().table().node()); } ') 
      ) 
      )
  output$debug<-renderTable({
    cbind(DF()[,-6],shinyValue('adj',nrow(iris)),Petal_Area=iris$Petal.Length*iris$Petal.Width/shinyValue('adj',nrow(iris)))
  })
      } 

shinyApp(ui, server)

As soon as I add the calculation, output from the DT does not find it's way into the debugging table.

On a personal note: I remember using this shinyInput and shinyValue trick about half a year ago. I also remember that it was very very unstable. I would not recommend it to anyone who wants to develop a stable app

I also remember that there was another R-package for complete interactive tables. It is called rhandsontables. Maybe try that: https://jrowen.github.io/rhandsontable/