recreating a lexis grid using ggplot

I am following up to an answer I got to this question on creating a lexis grid. While the answer got me to the point where I could overlay my data with a lexis grid, due to the density of my data, the lexis grid was completely obscured by the fill. I got a hacky sort of response for bringing the grid to the front with the solution:

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

This worked initially, however, as I added more detail to the plot that created more layers, it sort of fell apart as a solution.

So I am now trying to completely circumvent the lexis_grid command and the LexisPlotR package. Instead, I just want to add a sequence of vertical, horizontal, and diagonal lines.

What I want is along the lines of the following image, from this article:

This is what I am trying:

library('dplyr')
library('ggplot2')
library('viridis')

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")


ggplot(df, aes(x=year, y=age, fill=event)) +
  geom_tile() +
  scale_fill_viridis() + 
  geom_hline(yintercept=seq(0, 80, by=10)) +
  geom_vline(xintercept=seq(1900,2030, by=10)) +
  geom_abline(intercept=seq(0, 80, by=10), slope=1) + 
  labs(fill = "Count",
       title = "Events")

Which gets me the following:

The problem is, I don't know why there are dots below the 0 line and to the left of the 1900 line. And I have no idea what I'm doing wrong with the geom_abline, but I can't get the diagonals to work for anything.

The reason the tiles fill to the left of 1900 and below 0 is that the tiles are centered on the x/y coordinates, and they spill out in all directions based in width/height. I don't know of any way of showing dots with finite size that don't visually appear to spill out outside of the domain of values.

The reason your ablines do not show is that your intercept is assuming a 0,0 origin on the plot, but your x axis starts at 1900. The "real" (y-)intercept is far below 0; 1900 below, to be precise. If we accommodate that (and widen the range a bit), we can see the diagonal lines.

Reproducible data (using set.seed) and correcting for the unadvised use of <- inside of data.frame:

library('dplyr')
library('ggplot2')
library('viridis')
set.seed(42)
df <- data.frame(
  year  = sample(c(1900:2021), 1000, TRUE),
  age   = sample(c(0:80), 1000, TRUE),
  event = sample(c(0:5), 1000, TRUE)
)
head(df)
#   year age event
# 1 1948  66     1
# 2 2000  13     4
# 3 1964  72     0
# 4 1924  55     1
# 5 1973  43     2
# 6 1999  54     1

ggplot(df, aes(x=year, y=age, fill=event)) +
  geom_tile() +
  scale_fill_viridis() + 
  geom_hline(yintercept=seq(0, 80, by = 10)) +
  geom_vline(xintercept=seq(1900, 2030, by = 10)) +
  geom_abline(intercept=seq(0, 200, by = 10) - 2020, slope = 1) + 
  labs(fill = "Count", title = "Events")

The use of seq(0, 200, by = 10) is because we have 80/10=8 lines to draw originating from the left-border, and (2020-1900)/10=12 lines to draw originating from the bottom-border. You can change to seq(-10, 200, by = 10) - 2020 to fill in that last diagonal. It's okay to over-draw some ablines, they will be optimized out of the plot. (For instance, seq(-50, 300, by = 10) - 2020 works without otherwise affecting the x/y limits.)