Exclude line/points from showing info when using add_tooltip with hover in ggvis

Question

I've been playing around with the nice ggvis package. I'm doing a custom linear regression and wanted a tooltip to show info about each data point. However, when I add my regression line, the tooltip appears when I hover over the line, and shows then the info about the first datapoint (see screenshot). I provide this simple reproducible example:

library(ggvis)
mtc <- mtcars
lm=with(mtc,lm(mpg~wt))
mtc$fit=lm$coefficients[1]+mtcars$wt*lm$coefficients[2]
mtc$id <- 1:nrow(mtc)  # Add an id column to use ask the key

all_values <- function(x) {
    if(is.null(x)) return(NULL)
    row <- mtc[mtc$id == x$id, ]
    paste0(names(row), ": ", format(row), collapse = "
           ")
}

mtc %>% ggvis(x = ~wt, y = ~mpg, key := ~id) %>%
    layer_points() %>%layer_lines(x= ~wt,y= ~fit)%>% 
    add_tooltip(all_values, "hover")

This produces this

I would like to exclude the regression line from the tooltip so it only shows info about the data points. Is there a way to achieve this? Thank you for your help!

Answer 1

After a bit of playing around I got it to work.

First of all I needed to construct two separate data sets for this to work. One for the linear model data and one for the mtcars.

Solution

Constructing the data

mtc <- mtcars
mtc$id <- 1:nrow(mtc) 

lm=with(mtc,lm(mpg~wt))
df=data.frame(fit=lm$coefficients[1]+mtcars$wt*lm$coefficients[2])
df$id <- 101:132
df$wt <- mtcars$wt

As you can see above mtc is the data with the mtcars data and df is the linear model data. Notice that in the df I added an id column all of its values are greater than 100 and also completely different to the mtc data.frame.

Whenever you hover over points all_values will access the id column from mtc and whenever you hover over the line all_values will access the id column from df.

I added a line to your function below which is what makes it work:

all_values <- function(x) {
  #if the id is greater than 100 i.e. the df data.frame
  #then return NULL
  if(x$id>100) return(NULL)
  if(is.null(x)) return(NULL)
  row <- mtc[mtc$id == x$id, ]
  paste0(names(row), ": ", format(row), collapse = "
           ")
}

Then plot two separate data.frames. the add_tooltip will find the id variable for for both data.frames:

ggvis(x=~wt) %>%
     layer_points(data=mtc, y = ~mpg, key := ~id) %>%
     layer_paths(data=df,y= ~fit, key := ~id) %>%
     add_tooltip(all_values, "hover")

I cannot show the full interactivity with this graph but you can see in the pic below that although my cursor is above the line no info is shown.

Whereas the points do show the info when hovered over.