For each x value, geom_ribbon()
displays a y interval defined
by ymin
and ymax
. geom_area()
is a special case of
geom_ribbon()
, where the ymin
is fixed to 0 and y
is used instead
of ymax
.
Usage
geom_ribbon(
mapping = NULL,
data = NULL,
stat = "identity",
position = "identity",
...,
na.rm = FALSE,
orientation = NA,
show.legend = NA,
inherit.aes = TRUE,
outline.type = "both"
)
geom_area(
mapping = NULL,
data = NULL,
stat = "align",
position = "stack",
na.rm = FALSE,
orientation = NA,
show.legend = NA,
inherit.aes = TRUE,
...,
outline.type = "upper"
)
stat_align(
mapping = NULL,
data = NULL,
geom = "area",
position = "identity",
...,
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE
)
Arguments
- mapping
Set of aesthetic mappings created by
aes()
. If specified andinherit.aes = TRUE
(the default), it is combined with the default mapping at the top level of the plot. You must supplymapping
if there is no plot mapping.- data
The data to be displayed in this layer. There are three options:
If
NULL
, the default, the data is inherited from the plot data as specified in the call toggplot()
.A
data.frame
, or other object, will override the plot data. All objects will be fortified to produce a data frame. Seefortify()
for which variables will be created.A
function
will be called with a single argument, the plot data. The return value must be adata.frame
, and will be used as the layer data. Afunction
can be created from aformula
(e.g.~ head(.x, 10)
).- stat
The statistical transformation to use on the data for this layer, either as a
ggproto
Geom
subclass or as a string naming the stat stripped of thestat_
prefix (e.g."count"
rather than"stat_count"
)- position
Position adjustment, either as a string naming the adjustment (e.g.
"jitter"
to useposition_jitter
), or the result of a call to a position adjustment function. Use the latter if you need to change the settings of the adjustment.- ...
Other arguments passed on to
layer()
. These are often aesthetics, used to set an aesthetic to a fixed value, likecolour = "red"
orsize = 3
. They may also be parameters to the paired geom/stat.- na.rm
If
FALSE
, the default, missing values are removed with a warning. IfTRUE
, missing values are silently removed.- orientation
The orientation of the layer. The default (
NA
) automatically determines the orientation from the aesthetic mapping. In the rare event that this fails it can be given explicitly by settingorientation
to either"x"
or"y"
. See the Orientation section for more detail.- show.legend
logical. Should this layer be included in the legends?
NA
, the default, includes if any aesthetics are mapped.FALSE
never includes, andTRUE
always includes. It can also be a named logical vector to finely select the aesthetics to display.- inherit.aes
If
FALSE
, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g.borders()
.- outline.type
Type of the outline of the area;
"both"
draws both the upper and lower lines,"upper"
/"lower"
draws the respective lines only."full"
draws a closed polygon around the area.- geom
The geometric object to use to display the data, either as a
ggproto
Geom
subclass or as a string naming the geom stripped of thegeom_
prefix (e.g."point"
rather than"geom_point"
)
Details
An area plot is the continuous analogue of a stacked bar chart (see
geom_bar()
), and can be used to show how composition of the
whole varies over the range of x. Choosing the order in which different
components is stacked is very important, as it becomes increasing hard to
see the individual pattern as you move up the stack. See
position_stack()
for the details of stacking algorithm. To facilitate
stacking, the default stat = "align"
interpolates groups to a common set
of x-coordinates. To turn off this interpolation, stat = "identity"
can
be used instead.
Orientation
This geom treats each axis differently and, thus, can thus have two orientations. Often the orientation is easy to deduce from a combination of the given mappings and the types of positional scales in use. Thus, ggplot2 will by default try to guess which orientation the layer should have. Under rare circumstances, the orientation is ambiguous and guessing may fail. In that case the orientation can be specified directly using the orientation
parameter, which can be either "x"
or "y"
. The value gives the axis that the geom should run along, "x"
being the default orientation you would expect for the geom.
Aesthetics
geom_ribbon()
understands the following aesthetics (required aesthetics are in bold):
x
ory
ymin
orxmin
ymax
orxmax
alpha
colour
fill
group
linetype
linewidth
Learn more about setting these aesthetics in vignette("ggplot2-specs")
.
See also
geom_bar()
for discrete intervals (bars),
geom_linerange()
for discrete intervals (lines),
geom_polygon()
for general polygons
Examples
# Generate data
huron <- data.frame(year = 1875:1972, level = as.vector(LakeHuron))
h <- ggplot(huron, aes(year))
h + geom_ribbon(aes(ymin=0, ymax=level))
h + geom_area(aes(y = level))
# Orientation cannot be deduced by mapping, so must be given explicitly for
# flipped orientation
h + geom_area(aes(x = level, y = year), orientation = "y")
# Add aesthetic mappings
h +
geom_ribbon(aes(ymin = level - 1, ymax = level + 1), fill = "grey70") +
geom_line(aes(y = level))
# The underlying stat_align() takes care of unaligned data points
df <- data.frame(
g = c("a", "a", "a", "b", "b", "b"),
x = c(1, 3, 5, 2, 4, 6),
y = c(2, 5, 1, 3, 6, 7)
)
a <- ggplot(df, aes(x, y, fill = g)) +
geom_area()
# Two groups have points on different X values.
a + geom_point(size = 8) + facet_grid(g ~ .)
# stat_align() interpolates and aligns the value so that the areas can stack
# properly.
a + geom_point(stat = "align", position = "stack", size = 8)
# To turn off the alignment, the stat can be set to "identity"
ggplot(df, aes(x, y, fill = g)) +
geom_area(stat = "identity")