goem_bar() can't add 1-row data.frame with POSIXct-Date in x-axes

[the-Hull]

Dear devs,

I've encountered behaviour with geom_bar() which may be a bug. I noticed the behaviour in a bar chart, where the x-axes contained POSIXct dates, while trying to highlight a single year by adding a new layer with a subsetted data.frame with nrow == 1. The expected chart is generated when using a data.frame with length > 1 (see reprex). The behaviour does not ocurr with numeric x values and axis.
The issue may be related to #2047.

Thanks,
Alex

library(ggplot2)
#> Warning: package 'ggplot2' was built under R version 4.2.3

# with posixct axis --------------------------------------------------------

start <- as.POSIXct("2020-01-01")
end <- as.POSIXct("2030-01-01")
dates <- seq(start, end, length.out = 11)

values <- (1:11)

df <- data.frame(date = dates, value = values)


filter_date_single_row <- "2029-01-01"
# assert that we will try to add a df with a single row
if(nrow(df[df$date > as.POSIXct(filter_date_single_row), ]) == 1){

    ggplot(df) +
        geom_bar(aes(x = date, y = value, fill = "base"), stat = "identity") +
        # add single row
        geom_bar(
            inherit.aes = FALSE,
            data = df[df$date > as.POSIXct(filter_date_single_row), ],
            aes(x = date, y = value, fill = "add"),
            stat = "identity")
}

filter_date_multiple <- "2025-01-01"
# assert that we will try to add a df with more than one row row
if(nrow(df[df$date > as.POSIXct(filter_date_multiple), ]) > 1){

    ggplot(df) +
        geom_bar(aes(x = date, y = value, fill = "base"), stat = "identity") +
        # add single row
        geom_bar(
            inherit.aes = FALSE,
            data = df[df$date > as.POSIXct(filter_date_multiple), ],
            aes(x = date, y = value, fill = "add"),
            stat = "identity")
}

str(df[df$date > as.POSIXct(filter_date_single_row), ])
#> 'data.frame':    1 obs. of  2 variables:
#>  $ date : POSIXct, format: "2030-01-01"
#>  $ value: int 11
str(df[df$date > as.POSIXct(filter_date_multiple), ])
#> 'data.frame':    5 obs. of  2 variables:
#>  $ date : POSIXct, format: "2025-12-31 19:12:00" "2027-01-01 02:24:00" ...
#>  $ value: int  7 8 9 10 11

# with numeric X-Axis -----------------------------------------------------


x <- 1:11
values <- (1:11)
df <- data.frame(x = x, value = values)


# this works
filter_x_single_row <- 10
# assert that we will try to add a df with a single row
if(nrow(df[df$x > filter_x_single_row, ]) == 1){

    ggplot(df) +
        geom_bar(aes(x = x, y = value, fill = "base"), stat = "identity") +
        # add single row
        geom_bar(
            inherit.aes = FALSE,
            data = df[df$x > filter_x_single_row, ],
            aes(x = x, y = value, fill = "add"),
            stat = "identity")
}

^{Created on 2024-09-26 with reprex v2.1.1}

ggplot2 Version: 3.5.1
R: 4.2.2

[teunbrand]

You are adding the data without any problems, it is just that there is no reasonable way to determine a good width from the data (and hence the solo bar becomes very thin). If you set that manually, it should work as intended. However, I don't think there is an easy way to set a date-width, so in the example below I've opted for the awkward 28405728.

library(ggplot2)

start <- as.POSIXct("2020-01-01")
end <- as.POSIXct("2030-01-01")
dates <- seq(start, end, length.out = 11)

values <- (1:11)

df <- data.frame(date = dates, value = values)

filter_date_single_row <- "2029-01-01"

ggplot(df) +
  geom_bar(aes(x = date, y = value, fill = "base"), stat = "identity") +
  geom_col(
    data = df[df$date > as.POSIXct(filter_date_single_row), ],
    aes(x = date, y = value, fill = "add"), width = 28405728
  )

^{Created on 2024-09-26 with reprex v2.1.1}

[the-Hull]

Thanks for the hint - I was wondering if this was the issue and had been tinkering with width, also using resolution(). There I was only passing the original dates, which resulted in a width of one. But using resolution(as.numeric(df$date)) gives what appears to be the correct value in a similiar order of magnitude as in your example. I will close the issue - thank you! Do you reckon a warning message or hint for geom_bar/col when adding a layer with length-1 POSIXct data would be useful? Something along the lines of "The width of your bar is possibly off. Consider setting it manually, for example, with resolution()?