ggvis barplot: negative values

Question

I'm trying to draw a barplot using ggvis, for some data where for each variable I have both a negative and a positive value. It would be similar to this example from ggplot2.

However, when I try something similar in ggvis, I end up with basically no plot at all, just some weird lines.

Example data:

df <- data.frame(
direction=rep(c("up", "down"), each=3),
value=c(1:3, -c(1:3)),
x=rep(c("A", "B", "C"), 2))

This works, for all positive values:

df %>%
mutate(value.pos=abs(value)) %>%
ggvis(x=~x, y=~value.pos) %>%
group_by(direction) %>%
layer_bars(stack=TRUE)

This gives me nothing:

df %>%
ggvis(x=~x, y=~value) %>%
group_by(direction) %>%
layer_bars(stack=TRUE)

I've also tried various combinations of plotting them one by one, e.g.:

df %>%
spread(key=direction, value=value) %>%
ggvis(x=~x, y=~up) %>%
layer_bars() %>%
layer_bars(x=~x, y=~down)

So far, no luck. I suspect I'm missing some simple solution...

score 0 · Answer 1 · answered Aug 03 '16 at 07:49

I don't ggvis lets you produce stacked bar plots with negative values within the same groups as positive data.

This is because if an x value appear more than once in the data, then ggvis will sum up the y values at each x. I had thought that since you plotted the vector 1:3, they canceled out, but that's not the case.

As of now, I do not believe that dodged bar plots exist for this. It also messes with the labels.

You can produce the plot non-stacked, while filling in the position.

df %>%
  group_by(direction) %>%
  ggvis(x=~x, y=~value, fill = ~direction) %>%
  layer_bars(stack = FALSE)

Anyways, you might consider avoiding ggvis for any production work since it is under development, and hasn't been updated in a couple of months.

score 0 · Answer 2 · answered Aug 03 '16 at 23:32

@shayaa Thanks, this does seem to be working, although it will probably require some tweaking, and may not look as nicely as if I was using ggplot2. Actually, the reason I am using ggvis, is because I would like to combine it with shiny, to make a small interactive web version. For example:

df <- data.frame(
    direction=rep(c("up", "down"), each=3),
    value=c(1:3, -c(1:3)),
    x=rep(c("A", "B", "C"), 2))

plot_fct <- function(letter) {
    df %>%
        filter(x==letter) %>%
        ggvis(x=~x, y=~value, fill = ~direction) %>%
        layer_bars(stack = FALSE) %>%
        scale_numeric("y", domain=c(NA,NA))
}

ui <- fluidPage(
    sidebarPanel(
        selectInput("letter", "Choose letter", c("A", "B", "C"), selected="A")
    ),
    mainPanel(
        ggvisOutput("letter_barplot")
    )
)

server <- function(input, output) {
    plot_fct(letter=reactive(input$letter)) %>% bind_shiny("letter_barplot")
}   
runApp(shinyApp(ui, server))

However, it does not seem to work for me anyway, since there is some issue with the reactive being of class character. I keep getting the error:

Error in eval(substitute(expr), envir, enclos) : comparison (1) is possible only for atomic and list types

Guess I'll have to keep trying.

Absolutely. And hopefully the package gets some updates soon. In the meantime, you can click the checkmark next to my answer to indicate that this question is resolved. — shayaa, Aug 06 '16 at 07:18

ggvis barplot: negative values

2 Answers2