Creating an animated Christmas tree in R
With Christmas tomorrow we have decided to create an animated Christmas Tree using {ggplot2}, {sf} and {gganimate}.
First we need a tree. To do this we have used an {sf} polygon where we
pass in the coordinates of the Christmas tree as a list matrix to
st_polygon. We can then use geom_sf to add this layer onto a ggplot
object.
library(ggplot2)
library(gganimate)
library(sf)
tree_coords =
list(
matrix(
c(-4, 0,
-2.22, 2,
-3.5, 2,
-1.5, 4,
-2.5, 4,
-0.8, 6,
-1.5, 6,
0, 8,
1.5, 6,
0.8, 6,
2.5, 4,
1.5, 4,
3.5, 2,
2.22, 2,
4, 0,
-4, 0),
ncol=2, byrow=T
)
)
tree = st_polygon(tree_coords)
gg_tree = ggplot() +
geom_sf(aes(), data=tree)
gg_tree
Okay, so now we have a tree shape. Now we need to make it a little more Christmassy by changing:
- The color using:
fill = "forestgreen", color = "darkgreen" - Adding the trunk:
geom_rect(aes(xmin = -0.75, xmax = 0.75, ymin = -2, ymax = 0), fill = "saddlebrown", color = "sienna4") - Add a star on the top:
geom_point(aes(x = 0, y = 8), color = "gold", shape = 8, size = 7, stroke = 3) - Remove the axis with:
theme_void() - Set the border:
coord_sf(xlim = c(-6, 6), ylim = c(-4, 10)) - Add a Christmas message:
annotate("text", x = 0, y = 9.5, label = "Merry Christmas \n From Jumping Rivers!", size = 6)
Now our tree looks like this:
gg_tree = ggplot() +
geom_sf(aes(), data=tree, fill = "forestgreen", color = "darkgreen") +
geom_rect(aes(xmin = -0.75, xmax = 0.75, ymin = -2, ymax = 0), fill = "saddlebrown", color = "sienna4") +
geom_point(aes(x = 0, y = 8), color = "gold", shape = 8, size = 7, stroke = 3) +
theme_void() +
coord_sf(xlim = c(-6, 6), ylim = c(-4, 10)) +
annotate("text", x = 0, y = 9.5, label = "Merry Christmas \n From Jumping Rivers!", size = 6)
gg_tree
Next we need to use {sf} again to make some lights for the tree then {gganimate} to make the lights flash.
Placing the points within the boundaries of the tree was a trickier task
than we expected until we fell upon st_sample which we can pass a
polygon to and it’ll create some sample points within the boundaries. We
also create a vector to colour the points.
points = st_sample(tree, 75)
colours = sample(c("red", "yellow", "blue"), 75, replace = TRUE)
gg_tree = ggplot() +
geom_sf(aes(), data=tree, fill = "forestgreen", color = "darkgreen") +
geom_sf(aes(), data=points, color = colours) +
geom_rect(aes(xmin = -0.75, xmax = 0.75, ymin = -2, ymax = 0), fill = "saddlebrown", color = "sienna4") +
geom_point(aes(x = 0, y = 8), color = "gold", shape = 8, size = 7, stroke = 3) +
theme_void() +
coord_sf(xlim = c(-6, 6), ylim = c(-4, 10)) +
annotate("text", x = 0, y = 9.5, label = "Merry Christmas \n From Jumping Rivers!", size = 6)
gg_tree
We can now animate it to make the lights sparkle using transition_time
and ease_aes:
gg_tree +
transition_time(1:75) +
ease_aes('linear')
Lastly, have a great Christmas and New Year from the Jumping Rivers team!
