position_stack {ggplot2} | R Documentation

## Stack overlapping objects on top of each another

### Description

`position_stack()` stacks bars on top of each other; `position_fill()` stacks bars and standardises each stack to have constant height.

### Usage

    position_stack(vjust = 1, reverse = FALSE)

    position_fill(vjust = 1, reverse = FALSE)

### Arguments

`vjust` | Vertical adjustment for geoms that have a position (like points or lines), not a dimension (like bars or areas). Set to `0` to align with the bottom, `0.5` for the middle, and `1` (the default) for the top.
`reverse` | If `TRUE`, will reverse the default stacking order. This is useful if you're rotating both the plot and legend.

### Details

`position_fill()` and `position_stack()` automatically stack values in reverse order of the group aesthetic, which for bar charts is usually defined by the fill aesthetic (the default group aesthetic is formed by the combination of all discrete aesthetics except for x and y). This default ensures that bar colours align with the default legend.

There are three ways to override the defaults depending on what you want:

1. Change the order of the levels in the underyling factor. This will change the stacking order, and the order of keys in the legend.

2. Set the legend `breaks` to change the order of the keys without affecting the stacking.

3. Manually set the group aesthetic to change the stacking order without affecting the legend.

Stacking of positive and negative values are performed separately so that positive values stack upwards from the x-axis and negative values stack downward.

### See Also

See `geom_bar` and `geom_area` for more examples.

Other position adjustments: `position_dodge`, `position_identity`, `position_jitterdodge`, `position_jitter`, `position_nudge`

### Examples

    # Stacking and filling ------------------------------------------------------

    # Stacking is the default behaviour for most area plots.
    # Fill makes it easier to compare proportions
    ggplot(mtcars, aes(factor(cyl), fill = factor(vs))) +
      geom_bar()
    ggplot(mtcars, aes(factor(cyl), fill = factor(vs))) +
      geom_bar(position = "fill")

    ggplot(diamonds, aes(price, fill = cut)) +
      geom_histogram(binwidth = 500)
    ggplot(diamonds, aes(price, fill = cut)) +
      geom_histogram(binwidth = 500, position = "fill")

    # Stacking is also useful for time series
    series <- data.frame(
      time = c(rep(1, 4),rep(2, 4), rep(3, 4), rep(4, 4)),
      type = rep(c('a', 'b', 'c', 'd'), 4),
      value = rpois(16, 10)
    )
    ggplot(series, aes(time, value)) +
      geom_area(aes(fill = type))

    # Stacking order ------------------------------------------------------------

    # You control the stacking order by setting the levels of the underlying
    # factor. See the forcats package for convenient helpers.
    series$type2 <- factor(series$type, levels = c('c', 'b', 'd', 'a'))
    ggplot(series, aes(time, value)) +
      geom_area(aes(fill = type2))

    # You can change the order of the levels in the legend using the scale
    ggplot(series, aes(time, value)) +
      geom_area(aes(fill = type)) +
      scale_fill_discrete(breaks = c('a', 'b', 'c', 'd'))

    # Non-area plots ------------------------------------------------------------

    # When stacking across multiple layers it's a good idea to always set
    # the `group` aethetic in the ggplot() call. This ensures that all layers
    # are stacked in the same way.
    ggplot(series, aes(time, value, group = type)) +
      geom_line(aes(colour = type), position = "stack") +
      geom_point(aes(colour = type), position = "stack")

    ggplot(series, aes(time, value, group = type)) +
      geom_area(aes(fill = type)) +
      geom_line(aes(group = type), position = "stack")

    # You can also stack labels, but the default position is suboptimal.
    ggplot(series, aes(time, value, group = type)) +
      geom_area(aes(fill = type)) +
      geom_text(aes(label = type), position = "stack")

    # You can override this with the vjust parameter. A vjust of 0.5
    # will center the labels inside the corresponding area
    ggplot(series, aes(time, value, group = type)) +
      geom_area(aes(fill = type)) +
      geom_text(aes(label = type), position = position_stack(vjust = 0.5))

    # Negative values -----------------------------------------------------------

    df <- tibble::tribble(
      ~x, ~y, ~grp,
      "a", 1,  "x",
      "a", 2,  "y",
      "b", 1,  "x",
      "b", 3,  "y",
      "b", -1, "y"
    )
    ggplot(data = df, aes(x, y, group = grp)) +
      geom_col(aes(fill = grp), position = position_stack(reverse = TRUE)) +
      geom_hline(yintercept = 0)

    ggplot(data = df, aes(x, y, group = grp)) +
      geom_col(aes(fill = grp)) +
      geom_hline(yintercept = 0) +
      geom_text(aes(label = grp), position = position_stack(vjust = 0.5))

[Package ggplot2 version 2.2.1 Index]