dySliderInput plugin and minor bug fix

[jeffreyhanson]

dySliderInput

Overview

This pull request includes a dySliderInput plugin that turns dygraphs into a slider input widget. Check out this online demo at shinyapps.io. Dygraphs offers great potential for many plugins and I think it would be great if these were all available from this package so that users can easily access them. To that end, I have added functions for this plugin and the other plugins (dyUnzoom and dyCrosshair) so that users can use these plugins. It also fixes a bug in returning date-times from dygraphs.

How does dySliderInput work?

I have written a dygraphs plugin called dySliderInput in javascript. This plugin can be compiled using the dyPlugin function and added to an existing dygraph object. Once added to a dygraph object, users can click on the dygraph and a bar will be added to mark closest data point (which can be accessed programatically using input$dygraph_click$date). Additionally, users can animate the slider bar by clicking on the play button. The animation can be customised similar to that in shiny::sliderInput using the shiny::animationOptions function. This plugin is best used when in conjunction with other widgets. For instance, it could be used with the leaflet R package to show spatio-temporal data (as shown in the demo). This plugin is compatible with the dyRangeSelector. I have included the above demo as an example in the package.

Proposed usage of dySliderInput

#' dySliderInput
#' 
#' @inheritParams dyPlugin
#' @param color Color to draw slider. Defaults to 'red'.
#' @param strokePattern Line type for slider. Defaults to 'dashed'. Valid
#' arguments are 'dashed', 'solid', 'dotted', and 'dotdash'.
#' @param animate 'TRUE' to show simple animation controls with default 
#' settings; 'FALSE' not to; or a custom settings list, such as those
#' created using 'animationOptions'.
#'
#' @return A dygraph with the specified plugin enabled.
#'
#' @details The dySliderInput plugin turns the dyDygraph into a slider input
#' widget. The user can click on a point along the graph and the graph
#' will place a vertical line on the graph. The user can also use the animation
#' options to scroll through points along the graph.
#' 
#' @examples 
#' library(dygraphs)
#' dygraph(mdeaths) %>%
#'   dySliderInput()
#' 

List of changes

Here I will list all the changes I have made to this package, and my rationale behind them.

dySliderInput

• NAMESPACE: Now includes the dySliderInput function and functions it uses in other packages (grDevices::col2rgb, shiny::icon, and shiny::animationOptions).
• DESCRIPTION: The dySliderInput function uses the animationOptions and icon functions from shiny. Thus I have added 'shiny' to the imports section of the package. Additionally, because devtools::check() does not allow packages to listed under imports and enchances, I have removed shiny from enhances.
• R/plugins.R: I have added the dySliderInput function to allow users to add this plugin.
• tests/testthat/test-slider-input.R: This provides a test for the dySliderInput function.
• inst/examples/shiny_2: I have added the code for the dySliderInput demo here.
• inst/examples/plugins/sliderinput.js: This include the code for the dySliderInput plugin.

Bug fix

• inst/htmlwidgets/dygraphs.js:
  • Currently, when users click on a dygraph widget, this updates the input$dygraph_click and input$dygraph_date_window variables in a shiny session. The variables are based on a call to new Date(x) in javascript. However, just returning this can cause the returned dates to be incorrect.
  • Instead, to return the correct dates, a date-time string needs to be parsed manually after generating the Date object. To do this, I have included a shinyValueFormatter function that uses the function that generates x-axis labels (xValueFormatterFixedTZ or xValueFormatter) to correctly parse the string.
  • Additionally, since xValueFormatter originally made a call to Date().toLocaleString which uses different date-time formats depending on the environment, I have changed this to manually parse the same date-time format returned from xValueFormatterFixedTZ (but without the time-zone information).

DyUnzoom and dyCrosshair functions

• NAMESPACE: Now includes the dygraphs::dyCrosshair, dygraphs::dyUnzoom functions.
• R/plugins.R: I have added the dyCrosshair, dyUnzoom functions to allow users to add these plugins.
• tests/testthat/test-crosshair.R: This provides a test for the dyCrosshair function.
• tests/testthat/test-unzoom.R: This provides a test for the dyUnzoom function.

Miscellaneous

• I have added '.directory' and 'rsconnect' to the .gitignore to prevent these junk files from polluting the repository.

I really would like to see the dySliderInput widget incorporated into the dygraphs R package, so please let me know if you disagree with any of these changes, and I will update my PR accordingly.

[jjallaire]

This is a great PR and I very much look forward to merging it! I'm tied up this week but will have a look early the following week.

[przmv]

@jeffreyhanson Could you please divide your PR into several smaller ones to easier review and merge?

[jeffreyhanson]

I'm sorry I don't have any time to work on this for the foreseeable future. Please feel free to close this PR if needed.