This function will create polygons between two lines. If given a
temperature and theshold time series, like that produced by
detect_event
, the output will meet the specifications
of Hobday et al. (2016) shown as 'flame polygons.' If one wishes to
plot polygons below a given threshold, and not above, switch the values
being fed to the y
and y2
aesthetics. This function differs
in use from event_line
in that it must be created as a
ggplot
'geom' object. The benefit of this being that one may add
additional information to the figure as geom layers to ggplot2 graphs
as may be necessary.
geom_flame(
mapping = NULL,
data = NULL,
stat = "identity",
position = "identity",
...,
n = 0,
n_gap = 0,
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE
)
Set of aesthetic mappings created by aes()
or aes_()
.
If specified and inherit.aes = TRUE (the default), it is combined with the
default mapping at the top level of the plot. You must supply mapping if
there is no plot mapping.
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 to ggplot()
.
A data.frame, or other object, will override the plot data. All objects will
be fortified to produce a data frame. See fortify()
for which variables will
be created.
A function will be called with a single argument, the plot data. The return
value must be a data.frame
, and will be used as the layer data.
The statistical transformation to use on the data for this layer, as a string.
Position adjustment, either as a string, or the result of a call to a position adjustment function.
other arguments passed on to layer
. These are
often aesthetics, used to set an aesthetic to a fixed value, like
color = "red"
or linewidth = 3
. They may also be parameters
to the paired geom/stat.
The number of steps along the x-axis (i.e. in a daily time series this
would be days) required before the area between y
and y2
will be
filled in. The default of 0 will fill in _all_ of the area between the lines.
The standard to match Hobday et al. (2016) is n = 5
.
The number of steps along the x-axis (i.e. in a daily time series this
would be days) within which to allow geom_flame()
to connect polygons.
This is useful when one wants to not screen out parts of a polygon that dip
only briefly below y
before coming back up above it. The defauly of 0
will not connect any of the polygons. The standard to match
Hobday et al. (2016) is n_gap = 2
.
If FALSE
(the default), removes missing values with
a warning. If TRUE
silently removes missing values.
Logical. Should this layer be included in the legends? NA
,
the default, includes if any aesthetics are mapped. FALSE
never includes, and
TRUE
always includes. It can also be a named logical vector to finely select
the aesthetics to display.
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()
.
geom_flame
understands the following aesthetics (required aesthetics
are in bold):
x
y
y2
colour
fill
linewidth
alpha
linetype
Hobday, A.J. et al. (2016), A hierarchical approach to defining marine heatwaves, Progress in Oceanography, 141, pp. 227-238, doi: 10.1016/j.pocean.2015.12.014
event_line
for a non-ggplot2 based flame function.
ts <- ts2clm(sst_WA, climatologyPeriod = c("1983-01-01", "2012-12-31"))
res <- detect_event(ts)
mhw <- res$clim
mhw <- mhw[10580:10690,]
library(ggplot2)
ggplot(mhw, aes(x = t, y = temp)) +
geom_flame(aes(y2 = thresh)) +
geom_text(aes(x = as.Date("2011-02-01"), y = 28,
label = "That's not a heatwave.\nThis, is a heatwave.")) +
xlab("Date") + ylab(expression(paste("Temperature [", degree, "C]")))
#> Warning: All aesthetics have length 1, but the data has 111 rows.
#> ℹ Did you mean to use `annotate()`?