Rapid false gaussian plot with ggplot2

GaussianPlot.R

# Fast plot for gaussian function
#
library(ggplot2)
library(grid)
library(dplyr)
# Choose a window
seq = seq(-5, 5, 0.01)

# Compute density for Gaussian function
# Mean = 0, sd = 1
dens = dnorm(seq)
norm.dens = dens / max(dens)  # Normalized density

# Compute points of presence absence
int = seq(-5, 5, 0.5)
# If between -2 and 2 puts a 1 else a 0
pres.abs = mutate(as.data.frame(int), pres = ifelse(int > -2, ifelse(int < 2, 1, 0), 0))

ggplot(data.frame(seq, norm.dens), aes(x = seq, y = norm.dens)) +
  geom_line(size = 1.5, colour = "blue") +
  geom_point(data = pres.abs, size = 4, aes(x = int, y = pres)) +
  scale_y_continuous(breaks = c(0, 1)) +
  theme_classic() +
  labs(x = "Niche Axis (Ecological Variable)",
       y = "Species Presence or Absence") +
  annotate(geom = "segment", x = 0, xend = 0,
           y = 0.25, yend = 0.95, size = 2,
           arrow = arrow(length = unit(0.5,"cm")),
           color = "blue") +
  annotate("text", x = 0, y = 0.15, label = "Optimal Value\n=\nIndicator Value", lineheight = 0.6, color = "blue") +
  theme(axis.text = element_text(size = rel(1)))