overlay lexis_grid with heatmap - r

Question

I am trying to make a lexis_grid for a series of events for a synthetic cohorot of people aged 0:80 over the time period 1900-2021. What I'd like to get is something that looks a little like this:
Which I have taken from this article.
I have some dummy code created below:
library('dplyr')
library('LexisPlotR')
library('lubridate')
library('ggplot2')
df <- data.frame(
year <- sample(c(1900:2021), 1000, TRUE),
age <- sample(c(0:80), 1000, TRUE),
event <- sample(c(0:5), 1000, TRUE)
)
colnames(df) <- c("year", "age", "event")
mylexis <- lexis_grid(year_start = 1900,
year_end = 2021,
age_start = 0,
age_end = 80,
delta = 10
)
And I can create a heatmap in ggplot:
ggplot(df, aes(x = year, y = age, fill = event)) + geom_tile()
But I have been unsuccessful at combining them. These were my best guesses:
mylexis + geom_tile(df, mapping = aes(x = year(year), y = age, fill = event))
mylexis + ggplot(df, aes(x = year, y = age, fill = event)) + geom_tile()
Any advice on where to go from here?

Answer 1

One option would be to convert your year variable to a proper date:
library(ggplot2)
mylexis +
geom_tile(data = df, mapping = aes(x = as.Date(paste0(year, "-01-01")), y = age, fill = event))
EDIT A bit hacky but also a quick approach to change the order of the3 layers would be to manipulate the layers of the ggplot2 object like so, i.e. move the geom_tile (layer 3) to the first position (But I have to admit that at least for your example data the difference is hardly visible):
library(ggplot2)
p <- mylexis +
geom_tile(data = df, mapping = aes(x = as.Date(paste0(year, "-01-01")), y = age, fill = event))
p$layers <- p$layers[c(3, 1, 2)]
p