Using the downloadablePlot Shiny Module
In periscope: Enterprise Streamlined 'Shiny' Application Framework

Overview

Purpose

This Shiny Module was created in order to provide an easy-to-use downloadFileButton for a plot that is automatically created, linked and managed. This module is compatible with ggplot2, grob and lattice produced graphics as well as any superclass of these.

Features

Supports ggplot2, grob and lattice graphics and superclasses for maximum flexibility
Uses the downloadFile Shiny Module functionality to ensure consistent download functionality and paradigm for image or table data.
Ability to link different plot downloads from the displayed plot if desired (for example this might be used to ensure a watermark/copyright notice on downloaded plots)
Ability to add data downloads in addition to image downloads using the same button
Supports hover/click/brush functionality
Configurable plot size in application
Configurable plot aspect ratio for exported images
Configurable button placement at the bottom of the plot
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.

downloadablePlotUI

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

The downloadablePlotUI looks like:

The downloadablePlotUI function takes the unique object ID for the UI object. The next two arguments (downloadtypes and download_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 next two options (width, height) set the plot size in the UI and can be any css-recognizable size value. These options are followed with alignment and overlap options. The last three options give you the standard ways of interacting with shiny plots - using the functionality available with the clickOpts, hoverOpts and brushOpts functions. When you create an object using any of these functions shiny will send information about the user's interactions with the plot to the server and make it available to you via an input$ variable.

# Inside ui_body.R or ui_sidebar.R

downloadablePlotUI("object_id1", 
                   downloadtypes = c("png", "csv"), 
                   download_hovertext = "Download the plot and data here!",
                   height = "500px", 
                   btn_halign = "left")

downloadablePlot

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

the unique object ID that was provided to downloadablePlotUI 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
the aspect ratio as a numeric value for exported images of supported types.
The values are width:height (width/height which is unitless) for example for a 1:1 ratio (square) the value would be 1/1 = 1, for a 2:1 ratio (wide rectangle) the value would be 2/1 = 2, for 4:3 ratio (landscape photo) the value would be 4/3 = 1.33, etc. This value ensures an exported reasonable shape for a plot regardless of the size or shape of the application browser window.
a named list of functions that provide the images or data to the downloadFileButton (see below). It is important that the types of files to be downloaded are matched to the correct named function in the list. The functions are unquoted function names and will be called at the time the user initiates a download (see requirements below).
a function providing the plot output for the visible plot. It can be the same, or different, function as that provided to any of the download functions. This allows finer control over what the user can view vs. download if desired.

Download Function Requirements

The function must require NO parameters. No parameters will be provided when the function is called to retrieve the plot or data.
The function must return an appropriate data format for the file type. For instance: csv/tsv/xlsx types require data that is convertible to a tabular type, tiff requires a tiff class object, etc. For more information on conversion of data to various download types see the downloadFile module help or vignette. Note: For the visible plot the return value must be from the ggplot2, grob or lattice classes (or a superclass)
Since the function is called at the time the user requests the data it is acceptable and recommended to use reactive expressions providing dynamic values to the user from the application. All the above requirements apply.

# Inside server_local.R

downloadablePlot("object_id1",
                 logger = ss_userAction.Log,
                 filenameroot = "mydownload1",
                 aspectratio = 1.33,
                 downloadfxns = list(png = myplotfxn, tsv = mydatafxn),
                 visibleplot = myplotfxn)