Manipulating legend text in R plotly

Question

I have a data.frame I'd like to scatter plot using R's plotly with two factors which I'd like to color and shape by.

Here's my data:

set.seed(1)
df <- data.frame(x=rnorm(12),y=rnorm(12),
                 group=c(rep(1,3),rep(2,3),rep(3,3),rep(4,3)),
                 treatment=c(rep("A",6),rep("B",6)),
                 stringsAsFactors=F)

df$group <- factor(df$group,levels=1:4)
df$treatment <- factor(df$treatment,levels=c("A","B"))

Here's how I'm trying to plot:

require(plotly)

plot_ly(marker=list(size=10),type='scatter',mode="markers",x=~df$x,y=~df$y,color=~df$group,symbol=~df$treatment) %>% 
  add_annotations(text="group,treatment",xref="paper",yref="paper",x=1.02, xanchor="left",y=1.02,yanchor="top",legendtitle=TRUE,showarrow=FALSE) %>%
  layout(xaxis=list(title="x"),yaxis=list(title="y"))

which gives me:

Is it possible to get the text of group and treatment in the legend be separated by comma instead of the new line as it is now?

This means that instead of:

1

A

2

A

3

B

4

B

I'll have:

1,A

2,A

3,B

4,B

Answer 1

Sounds trivial but it's one of the cases where Plotly decides whats good for you.

The legend labels are composed of the categories of color and symbol which are all passed in one command. In order to get control over the output, let's add each trace separately.

for (grou in groups) {
  for (treat in treatments) {
    trace_data <- subset(df, group == grou & treatment == treat)
    if (nrow(trace_data) > 0) {
      p <- add_trace(p,
                     x = trace_data$x,
                     y = trace_data$y,
                     marker = list(size = 10,
                                   color = group,
                                   symbol = as.integer(charToRaw(treat)) - 65),
                     type = 'scatter',
                     mode = "markers",
                     name = paste(grou, treat, sep = ",")
                     )
    }
  }
}

We pass the color (not strictly necessary) via marker and symbol also via marker (both can be passed in the add_trace command as well but then again Plotly decides for you what do to do with it).

The legend label is passed via name.

Note: You need to convert your treatment explicitly because symbol expects either a named symbol or a number (unless your treatments are named diamond or circle)

Complete code

library(utils)
library(plotly)

set.seed(1)
df <- data.frame(x = rnorm(12),
                 y = rnorm(12),
                 group = c(rep(1, 3),
                           rep(2, 3),
                           rep(3, 3),
                           rep(4, 3)
                           ),
                 treatment=c(rep("A", 6),
                             rep("B", 6)
                             ),
                 stringsAsFactors = FALSE
                 )

groups <- unique(df$group)
treatments <- unique(df$treatment)

p <- plot_ly()
for (grou in groups) {
  for (treat in treatments) {
    trace_data <- subset(df, group == grou & treatment == treat)
    if (nrow(trace_data) > 0) {
      p <- add_trace(p,
                     x = trace_data$x,
                     y = trace_data$y,
                     marker = list(size = 10,
                                   color = group,
                                   symbol = as.integer(charToRaw(treat)) - 65),
                     type = 'scatter',
                     mode = "markers",
                     name = paste(grou, treat, sep = ",")
                     )
    }
  }
}
p <- add_annotations(p, 
                     text = "group,treatment",
                     xref = "paper",
                     yref = "paper",
                     x = 0.96, 
                     xanchor = "left",
                     y = 1.03,
                     yanchor = "top",
                     legendtitle = TRUE,
                     showarrow = FALSE) %>%
  layout(xaxis = list(title = "x"),
         yaxis = list(title = "y"))

p