The R plot_ly stacked bar chart can only show multiple values with different colors

Question

I am programming a R-application, where I need to visualize data in stacked bar-charts. So far everything works fine if there are multiple bars shown, but I am getting empty graphs when I want to show only one bar.

So I created different plots with some dummy data, that shows my problem. (The data is fictitious)

data <- data.table(FRUIT = c("apples", "bananas", "kiwis", "apples", "bananas", "kiwis"), 
                    KCALS = c(100, 200, 130, 100, 200, 130), 
                    DATE = as.Date(c("2022-10-01", "2022-10-01", "2022-10-01", "2022-10-02", "2022-10-03", "2022-10-03")))

The first graph shows an overview over multiple dates:

plot_ly(data, x = ~DATE, y = ~KCALS, color = ~FRUIT, type = "bar") %>%
    layout(yaxis = list(title = " "), xaxis = list(title = " "), barmode = "stack")

The second graph shows only one day:

plot_ly(data[DATE == "2022-10-01"], x = ~DATE, y = ~KCALS, type = "bar") %>%
    layout(yaxis = list(title = " "), xaxis = list(title = " "), barmode = "stack")

Ok, that worked. But if I enable the "color-option" again, the plot is empty:

plot_ly(data[DATE == "2022-10-01"], x = ~DATE, y = ~KCALS, color = ~FRUIT, type = "bar") %>%
    layout(yaxis = list(title = " "), xaxis = list(title = " "), barmode = "stack")

Why is it behaving like this? What am I doing wrong? And is there any documentation available, that really describes how the data gets processed in the plot_ly()- function?

Answer 1

When I run your code with color variable it does return a stacked bar plot for a single value. Make sure you don't overwrite variables and try it with a clean environment. Here is some reproducible code:

library(data.table)
data <- data.table(FRUIT = c("apples", "bananas", "kiwis", "apples", "bananas", "kiwis"), 
                   KCALS = c(100, 200, 130, 100, 200, 130), 
                   DATE = as.Date(c("2022-10-01", "2022-10-01", "2022-10-01", "2022-10-02", "2022-10-03", "2022-10-03")))
library(plotly)
plot_ly(data, x = ~DATE, y = ~KCALS, color = ~FRUIT, type = "bar") %>%
  layout(yaxis = list(title = " "), xaxis = list(title = " "), barmode = "stack")

plot_ly(data[DATE == "2022-10-01"], x = ~DATE, y = ~KCALS, type = "bar") %>%
  layout(yaxis = list(title = " "), xaxis = list(title = " "), barmode = "stack")

plot_ly(data[DATE == "2022-10-01"], x = ~DATE, y = ~KCALS, color = ~FRUIT, type = "bar") %>%
  layout(yaxis = list(title = " "), xaxis = list(title = " "), barmode = "stack")

^{Created on 2023-02-16 with reprex v2.0.2}

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Here you can find the docs about bar charts in plotly.