在 plotly R 中的 Boxplot 中显示数据点的最大值和最小值

Question

How can I display the values of minimum and maximum data points as text in boxplot which is plotted using plotly in R? Below is the sample reference to the code:

plot_ly(x = ~rnorm(50), type = "box") %>% add_trace(x = ~rnorm(50, 1))

Answer 1

You have to "switch" on the direction of the boxplot (min, max, median, q1, q3), as you plot horizontal boxplots.

plot_ly(x = ~rnorm(50), type = "box"
#-------------- set direction / switch on     
         , hoverinfo = "x") %>%    # let plotly know that x-direction give the hoverinfo
#----------------------------------------
   add_trace(x = ~rnorm(50, 1)) %>% 

#---------------- format label - here show only 2 digits
  layout(xaxis = list(hoverformat = ".2f"))  # again define for x-axis/direction!

amendment based on comment: add annotation

Plotly supports to add text as a trace(ie add_text() ) or as a layout option (ie annotations=list(...) ).
The annotation option provides support for offset, pointer arrow, etc.
Thus, I picked this option.

To be able to access the minimum and maximum values, I pull out the vector data definition. The labels combine the terms min and max with a 2-digit rounded value. Adapt this to your liking and possibly outside the plot. You can define vectors that you supply to the options of the annotation = list(...) call. Just pay attention to the sequence of the elements in the vector.

set.seed(1234)
x1 <- rnorm(50)
x2 <- rnorm(50, 1)

plot_ly(type = 'box', hoverinfo = "x") %>%
    add_trace(x = x1) %>%
    add_trace(x = x2) %>%
    layout(title = 'Box Plot',
           annotations = list(
           #------------- (x,y)-position vectors for the text annotation
               y = c(0,1),   # horizontal boxplots, thus 0:= trace1 and 1:= trace2
               x = c( min(x1), min(x2)   # first 2 elements reflect minimum values
                     ,max(x1), max(x2)   # ditto for maximum values
                     ),
           #------------- text label vector - simple paste of label & value
               text = c( paste0("min: ", round(min(x1),2)), paste0("min: ", round(min(x2),2)) 
                        ,paste0("max: ", round(max(x1),2)), paste0("max: ", round(max(x2),2)) 
                        ),
           #-------------- you can use a pointer arrow
               showarrow = TRUE
           #-------------- there are other placement options, check documentation for this
           )
    )