How to create plot with both vertical and horizontal spikelines in plotly?

Question

Plotly offers the option to display a moveable horizontal or vertical "spikeline" by adding layout(hovermode = "x unified") or layout(hovermode = "y unified") (see documentation). For example:

library(plotly)

x <- seq(from = 0, to = 2*pi, length = 100)
y <- sin(x)
fig <- plot_ly(x = x, y = y, type = "scatter", mode = "markers")
fig <- fig %>% layout(hovermode = "x unified")
fig

creates this plot with a vertical line that follows the cursor:

I would like to have both the vertical and the horizontal spikeline displayed. Like this:

I tried to modify the layout like this:

fig <- fig %>% layout(hovermode = "x unified") %>% layout(hovermode = "y unified")
# or
fig <- fig %>% layout(hovermode = c("x unified", "y unified"))
# or
fig <- fig %>% layout(hovermode = "x unified|y unified")

None of this worked. Would anybody have a suggestion?

Answer 1

You could use spikemode with the option across in your layout for both xaxis and yaxis. Here is a reproducible example:

library(plotly)

x <- seq(from = 0, to = 2*pi, length = 100)
y <- sin(x)
fig <- plot_ly(x = x, y = y, type = "scatter", mode = "markers")
fig %>%
  layout(xaxis = list(spikemode = 'across'),
         yaxis = list(spikemode = 'across'))

^{Created on 2022-10-29 with reprex v2.0.2}

As you can see both vertical and horizontal spike lines are shown.

---

If you only want to have the spike lines to your axis, you could use toaxis in your spikemode like this:

fig %>%
  layout(xaxis = list(spikemode = 'toaxis'),
         yaxis = list(spikemode = 'toaxis'))

^{Created on 2022-10-29 with reprex v2.0.2}

As you can see this only shows the spike lines to your axis.

Answer 2

Check out this resource on 3d plots - I had the same issue and applied the xaxis = list() and yaxis = list() arguments to layout() and it worked well for me.

https://plotly.com/r/3d-hover/