Add dynamic vertical line trace to plotly animated horizontal bar plot-CodePudding

I have a horizontal animated bar plot using the plotly package. I want to add a vertical line to show the median of the bar values and I want this to change value along with the frames of the bars.

Simplified example:

data <- data_frame(Year=c(1995, 1995, 1995, 1996, 1996, 1996, 1997, 1997, 1997, 1998, 1998, 1998),
                 Highest_Degree=c("Associate's", "Bachelor's", "PhD",
                                     "Associate's", "Bachelor's", "PhD",
                                     "Associate's", "Bachelor's", "PhD",
                                     "Associate's", "Bachelor's", "PhD"),
                 Salary=c(35200, 45270, 79670,
                             41950, 56330, 99410,
                             42780, 55930, 100000,
                             42860, 56080, 100000)
                 )

#plot 
plot_ly(data, x=~Salary, y=~Highest_Degree, frame=~Year, type = 'bar') %>%
layout(yaxis=list(title=" "), xaxis=list(title="Median Salary (USD)"),
       title=list(text=paste("Median Salary by Education Level 1995-1998")))

##to get medians list
medians <- data %>% 
select(c(Year, Salary)) %>%
group_by(Year) %>% 
summarise(Median=median(Salary))

Image example, except it needs to change with the rest of the animation:

UPDATE: I added the overall medians to my original data frame and added a horizontal line with a trace (image below), but the line doesn't span the entire height of the plot. Is there a way to do this with 'shapes' in layout when the y axis is not numeric so that it spans the entire plot?

CodePudding user response：

It might be easiest to start by building the plotly plot and manually modifying the frames' layouts. After that, I used vectorization to change the frames, so I wanted to ensure that the medians were in order by year. With such a small dataset, it's probably not necessary to do this by code, but I figured this is just a small snapshot of what you're working with.

# build to see frames
p2 <- plotly_build(p1)

# modify frames
# first, make sure the data is in order by year (order by frame)
medians <- arrange(medians, Year)

lapply(1:nrow(medians), # for each frame
       function(i){
         vline = list(
           type = "line",
           y0 = 0,
           y1 = 1,
           yref = "paper",
           x0 = unlist(medians[i, ]$Median), # median for that frame
           x1 = unlist(medians[i, ]$Median),
           line = list(color = "black", dash = "dot") # you can mod here!
           )
         p2$x$frames[[i]]$layout <<- list(shapes = list(vline)) # change plot
       })

After that, you can just call p2 to plot it.