R Shiny DT 数据表列宽适用于所有列，但不适用于特定列

Question

I have looked at the documentation, and examples, and other answers. But, for the life of me, I can't get the DT::datatable() to widen just one column in my output. When I set the option to include _all columns, it works, but obviously not what I want.

Here is a working example:

library(dplyr)
library(shiny)
library(DT)
library(data.table)

mtcars <- mtcars[1:5, ]

ui <- fluidPage(
  fluidRow(
    dataTableOutput(('mtcarsDT')),
    )
  )

server <- function(input, output, session) {
  output$mtcarsDT <- DT::renderDataTable({
    recFeedbackCol <- lapply(1:nrow(mtcars), function(recnum)
      as.character(
        radioButtons(
          paste0(
            'rec', recnum),
          '',
          choices = c('good' = 'Good', 'bad' = 'Bad', 'neutral' = 'Neutral'),
          inline = TRUE
        )
      )
    )
    recFeedbackCol <- tibble(feedback = recFeedbackCol)
    
    mtcars <- bind_cols(
      mtcars,
      recFeedbackCol
      )
    
    mtcars %>%
      DT::datatable(
        escape = FALSE, selection = 'none',
        extensions = 'FixedColumns',
        options = list(
          paging = FALSE, pageLength = 10, ordering = FALSE,  scrollX = TRUE,
          fixedColumns = list(leftColumns = 2),
          preDrawCallback = JS(
            'function() { Shiny.unbindAll(this.api().table().node()); }'
            ),
          drawCallback = JS(
            'function() { Shiny.bindAll(this.api().table().node()); } '
            ),
          autoWidth = TRUE,
          columnDefs = list(list(width = '200px', targets = 'feedback'))
          )
        )
    })
  }

shinyApp(ui = ui, server = server)

Changing targets = '_all' works. But, that widens all columns.

> packageVersion('shiny')
[1] ‘1.4.0’
> packageVersion('DT')
[1] ‘0.17’

Anything I am missing?

Update:

Now, I am using ncol(mtcars) and with some options, and the DT does not render at all. I get the columns, and zero rows in display:

library(dplyr)
library(shiny)
library(DT)
library(data.table)

mtcars <- mtcars[1:5, ]

ui <- fluidPage(
  fluidRow(
    dataTableOutput(('mtcarsDT')),
    )
  )

server <- function(input, output, session) {
  output$mtcarsDT <- DT::renderDataTable({
    recFeedbackCol <- lapply(1:nrow(mtcars), function(recnum)
      as.character(
        radioButtons(
          paste0(
            'rec', recnum),
          '',
          choices = c('good' = 'Good', 'bad' = 'Bad', 'neutral' = 'Neutral'),
          inline = TRUE
        )
      )
    )
    recFeedbackCol <- tibble(feedback = recFeedbackCol)
    
    mtcars <- bind_cols(
      mtcars,
      recFeedbackCol
      )
    
    mtcars %>%
      DT::datatable(
        extensions = 'FixedColumns',
        rownames = FALSE,
        escape = FALSE,
        class="compact cell-border",
        options = list(
          pageLength = 15, 
          lengthChange = FALSE, 
          scrollX = TRUE,
          searching = FALSE,
          dom = 't',
          ordering = TRUE,
          fixedColumns = list(leftColumns = 2),
          preDrawCallback = JS(
            'function() { Shiny.unbindAll(this.api().table().node()); }'
          ),
          drawCallback = JS(
            'function() { Shiny.bindAll(this.api().table().node()); } '
          ),
          autoWidth = TRUE,
          columnDefs = list(
            list(width = '200px', targets = ncol(mtcars))
          )
        )
      )
    })
  }

shinyApp(ui = ui, server = server)

Answer 1

For targets you can use a column index number (indexing is zero-based):

targets = 3

Or to target multiple specific columns, use an array:

targets = list(3,4)

There are some additional options, too - see here for reference.

---

Update

So, using the fact mentioned above about indexing being zero-based, and looking at the reference documentation (see the above link), we can say the following:

• The first column in the table has an index of 0.
• The second column in the table has an index of 1.
• ... and so on.

And we can also say:

• The last column in the table has an index of -1.
• The second-to-last column in the table has an index of -2.
• ... and so on.