How can I get tooltips showing in dygraphs without annotation

Question

I am trying to use the R implementation of dygraphs

The example provided is

library(dygraphs)

dygraph(presidents, main = "Presidential Approval") %>%
dyAxis("y", valueRange = c(0, 100)) %>%
dyAnnotation("1950-7-1", text = "A", tooltip = "Korea") %>%
dyAnnotation("1965-1-1", text = "B",  tooltip = "Vietnam")

which results in the chart

Hovering over the 'A' produces a tooltip with 'Korea'

I am keen to have a tooltip for every point preferably dispensing entirely with the text requirement - though setting text to "" with minimal height/width values might suffice. I would also want to attach the dyAnnotations programmatically from a file with date and tooltip columns

df <- data.frame(date=as.Date(c("1950-7-1","1965-1-1")),tooltip=c("Korea","Vietnam"))

Is this feasible,and, if so, how? TIA

Answer 1

Alright, as promised, here is a start to how we might use the legend for your information. We crudely overwrite the legend. This behavior can be made much more polite if you also want a legend. In addition, you could provide an object/hash with a data.frame to lookup the x and return an informative description.

I added a debugger so if you open your debugger in Chrome, etc. you can see what is happening.

library(dygraphs)

dyG = dygraph(presidents, main = "Presidential Approval") %>%
    dyAxis("y", valueRange = c(0, 100))

#  explore the legend route
dyG %>%
    dyCallbacks(
        highlightCallback = sprintf(
'function(e, x, pts, row) {

// added to illustrate what is happening
//   remove once satisfied with your code
debugger;  

var customLegend = %s

// should get our htmlwidget
e.target.parentNode.parentNode
  .querySelectorAll(".dygraph-legend")[0]
  .innerText = customLegend[row] + row;
}'
            ,# supply a vector or text that you would like
            jsonlite::toJSON(rep('something here',length(as.vector(presidents))))
        )
    )

Below, I have changed to add to the legend rather than replace.

#  explore the legend route
#    add to legend rather than replace
dyG %>%
  dyCallbacks(
    highlightCallback = sprintf(
      'function(e, x, pts, row) {

      // added to illustrate what is happening
      //   remove once satisfied with your code
      debugger;  

      var customLegend = %s


      // should get our htmlwidget
      var legendel = e.target.parentNode.parentNode
        .querySelectorAll(".dygraph-legend")[0];

      // should get our htmlwidget
      legendel.innerHTML = legendel.innerHTML + "<br>" + customLegend[row];
      }'
            ,# supply a vector or text that you would like
      jsonlite::toJSON(rep('something here',length(as.vector(presidents))))
    )
  )