How to add exactly same right axis on plotly R chart?

Question

I have this basic script:

mtcars %>%
  plot_ly() %>%
  add_trace(x = ~mpg, y = ~wt, type = 'scatter', mode = 'markers' ) %>%
  layout(yaxis2 = list(overlaying = "y", side = "right", title = 'test'))

It plots the chart with one axe on the left even though there is a command in layout to add a second chart.

I suppose it doesn't get triggered because nothing is plotted.

So I add the same variable

mtcars %>%
  plot_ly() %>%
  add_trace(x = ~mpg, y = ~wt, type = 'scatter', mode = 'markers' ) %>%
   add_trace(x = ~mpg, y = ~wt, type = 'scatter', mode = 'markers', yaxis = "y2" )  %>%
  layout(yaxis2 = list(overlaying = "y", side = "right", title = 'test'))

And in this case both left and right axis are the same. I suppose I could just do the second series transparent or something.

Is there a more clean solution to force the second axis to show even though nothing is plotted on it?

Answer 1

Try something like this:

library(plotly)
#Code
mtcars %>%
  plot_ly() %>%
  add_trace(x = ~mpg, y = ~wt, type = 'scatter', mode = 'markers' ) %>%
  add_trace(x = ~mpg, y = ~wt, type = 'scatter', mode = 'markers',
            yaxis = "y2") %>%
  layout(yaxis2 = list(overlaying = "y", side = "right", title = 'test'))

Output:

Answer 2

Old question, but anyway:

You can't display an axis without assigning a trace to it.

However, you don't need to use the entire data again - you can simply create datapoints based on range() to achive the same an hide the trace via the opacity and showlegend parameters (using visible would prevent showing the axis):

library(plotly)

mtcars %>%
  plot_ly() %>%
  add_trace(x = ~mpg, y = ~wt, type = 'scatter', mode = 'markers') %>%
  add_trace(x = ~range(mpg), y = ~range(wt), type = 'scatter', mode = 'markers', yaxis = "y2", opacity = 0, showlegend = FALSE) %>%
  layout(showlegend = TRUE, yaxis2 = list(overlaying = "y", side = "right", title = 'test'))