Author: Dr. Connie Brett
Date: 2023-11-06

# Using the downloadableTable Shiny Module

#### Dr. Connie Brett

#### 2023-11-06

# Overview

## Purpose

This Shiny Module was created in order to provide a consistent-looking and easy-to-use table including a downloadFileButton that is automatically created, linked and managed.

## Features

- Uses the downloadFile Shiny Module functionality to ensure consistent download functionality and paradigm for the table data.
- Ability to link different data sets to the displayed table and downloadFile functionality if desired
- User selection of multiple rows by default - can be single select also by setting the appropriate option
- Returns a reactive expression containing the rows of the table selected by the user
- Supports full-table searching including regular expressions with search highlighting
- Columns are sortable in both directions
- Configurable table “window” (viewing area) height with infinite vertical scrolling (no paging)
- Supports rownames and a table caption
- Requires minimal code (see the Usage section for details)

# Usage

## Shiny Module Overview

Shiny modules consist of a pair of functions that modularize, or package, a small piece of reusable functionality. The UI function is called directly by the user to place the UI in the correct location (as with other shiny UI objects). The module server function that is called only once to set it up using the module name as a function inside the server function (i.e. user-local session scope. The function first arguments is string represents the module id (the same id used in module UI function). Additional arguments can be supplied by the user based on the specific shiny module that is called. There can be additional helper functions that are a part of a shiny module.

The downloadableTable Shiny Module is a part of the periscope package and consists of the following functions:

- downloadableTableUI - the UI function to place the table in the application
- downloadableTable - the server function to be called inside server_local.R.

## downloadableTableUI

The downloadableTableUI function is called from the ui.R (or equivalent) file in the location where the table should be placed. This is similar to other UI element placement in shiny.

The downloadableTableUI looks like:

The downloadableTableUI function takes the unique object ID for the UI object. The next two arguments (downloadtypes and hovertext) are passed to the downloadFileButton and set the file types the button will allow the user to request and the downloadFileButton’s tooltip text. The contentHeight argument is optional but important - it sets the viewable height of the table content which can be any css-recognizable size value.

downloadableTables are multi-select by default, however if you need a table to only allow single row selections you can set the singleSelect argument to TRUE.

    # Inside ui_body.R or ui_sidebar.R

    downloadableTableUI("object_id1",
                        downloadtypes = c("csv", "tsv"),
                        hovertext = "Download the data here!",
                        contentHeight = "300px",
                        singleSelect = FALSE)

## downloadableTable

The downloadableTable function is called directly. The call consists of the following:

- the unique object ID that was provided to downloadableTableUI when creating the UI object
- the logging logger to be used
- the root of the downloaded file name to be used in the browser as a character string or a reactive expression that returns a character string
- a named list of functions that provide the data to the downloadFileButton (see below). It is important that the types of files to be downloaded are matched to the correct data function in the list. The data functions are unquoted function names. The functions will be called at the time the user initiates a download (see requirements below).
- a data function providing the data for the visible table. It can be the same, or different, data as that provided by the download data functions. This allows finer control over what the user can view vs. download if desired.
- … free parameters named list to pass table customization options. It supports most of DT table options customization. See example below.

Data Function Requirements

- The function must require NO parameters. No parameters will be provided when the function is called to retrieve the data.
- The function must return an appropriate data format for the file type. For instance, for csv/tsv/xlsx types the data returned should be convertible to a tabular type. Note: For data shown in the table the data must be able to be converted to tabular format.
- Since the function is called at the time the user requests the data it is acceptable and recommended to use reactive expressions providing dynamic data to the user from the application. All the above requirements apply.

Reactive Return Value

The server function returns a reactive expression containing the selected rows (data, not references, rownumbers, etc - the actual table row data). This allows the user to capture this to update another table, chart, etc. as desired. It is acceptable to ignore the return value as well if this functionality is not needed.

Customization Options

downloadableTable module can be customized using the same `?DT::datatable` arguments. options or format functions. These options can be sent as a named options via the server function, see example below. Notes:

- `selection` parameter in the server function has different usage than `DT::datatable` `selection` option as it should be a function or reactive expression providing the row_ids of the rows that should be selected. Its default value is `NULL`
- `editable`, `width`, `height` options in `DT::datatable` are not supported

The following is an example of a customized downloadableTable:

It is generated using the following code:

    # Inside server_local.R
    sketch <- htmltools::withTags(table(
        class = "display",
        thead(
            tr(
                th(rowspan = 2, "Location"),
                th(colspan = 2, "Statistics")
            ),
            tr(
                th("Change"),
                th("Increase")
            )

        )
    ))

    selectedrows <- downloadableTable("exampleDT1",
                                      ss_userAction.Log,
                                      "exampletable",
                                      list(csv = load_data3, tsv = load_data3),
                                      load_data3,
                                      colnames = c("Area", "Delta", "Increase"),
                                      filter = "bottom",
                                      callback = htmlwidgets::JS("table.order([1, 'asc']).draw();"),
                                      container = sketch,
                                      formatStyle = list(columns = c("Total.Population.Change"),
                                                         color = DT::styleInterval(0, c("red", "green"))),
                                      formatStyle = list(columns = c("Natural.Increase"),
                                                         backgroundColor = DT::styleInterval(
                                                             c(7614, 15914, 34152),
                                                             c("blue", "lightblue", "#FF7F7F", "red"))))

    # NOTE: selectedrows is the reactive return value, captured for later use

## Sample Application

For a complete running shiny example application using the downloadableTable module you can create and run a periscope sample application using:

    library(periscope)

    app_dir = tempdir()
    create_new_application('mysampleapp', location = app_dir, sampleapp = TRUE)
    runApp(paste(app_dir, 'mysampleapp', sep = .Platform$file.sep))

# Additional Resources

Vignettes

- New Application
- downloadFile Module
- downloadablePlot Module