How to include greek letters and bold characters in a legend using plotly?

Question

I am trying to make a graph with greek letters in the legend and bold characters in the legend of the x-axis. This works fine with ggplot:

library(ggplot2)
library(plotly)
## Dataframe
df <- data.frame(dose=c("D0.5", "D1", "D2"),len=c(4.2, 10, 29.5))

## Legend with the greek letter pi
my.labs <- list(bquote(Pi==.(5)) )

## Plot with ggplot
p=ggplot(data=df, aes(x=dose, y=len, group=1,colour = paste("Pi = ",5,sep=""))) +
geom_line()+
geom_point()+
scale_colour_manual(values=3, labels=my.labs)+
theme(legend.title=element_blank(), legend.position = c(.1, .9),axis.title.x = element_text(face="bold", colour="black", size=10))

p

However the greek letter and the bold legend for the x-axis disappear when using plotly:

p=plotly_build(p)
style( p, hoverinfo = "x+y" ) %>% 
layout( legend = list(x = 0.1, y = 0.9, font=list(size=12)) )

Answer 1

You would need two small changes to get pretty close to your ggplot graph.

Set the xaxis title to bold manually

layout(legend = list(x = 0.1, 
                     y = 0.9, 
                   font=list(size=12)),
       xaxis = list(title = "<b>dose</b>")
)

Use the HTML code for pi in ggplot (works with RStudio in Windows) or add π (works with RStudio in Ubuntu).

colour = paste("π = ",5,sep="")

or

colour = paste("π = ",5,sep="")

---

library(ggplot2)
library(plotly)
## Dataframe
df <- data.frame(dose=c("D0.5", "D1", "D2"),len=c(4.2, 10, 29.5))

## Legend with the greek letter pi
my.labs <- list(bquote(Pi==.(5)) )

## Plot with ggplot
p=ggplot(data=df, aes(x=dose, y=len, group=1,colour = paste("&pi; = ",5,sep=""))) +
  geom_line()+
  geom_point()+
  scale_colour_manual(values=3, labels=my.labs)+
  theme(legend.title=element_blank(), legend.position = c(.1, .9),axis.title.x = element_text(face="bold", colour="black", size=10))
p
p=plotly_build(p)
p <- style(p, hoverinfo = "x+y" ) %>% 
  layout(legend = list(x = 0.1, 
                       y = 0.9, 
                       font=list(size=12)),
         xaxis = list(title = "<b>dose</b>")
  )

p