tornado_plot.R

library(tidyverse)
library(patchwork)

tornado <- tibble(x = 1:10,
                  y = c(2, 4, 5, 5.5, 4, 6, 7.5, 8, 7.5, 9)) %>% 
  mutate(dy = y - lag(y))

plot1 <- ggplot(tornado, aes(x = x, y = y)) +
  geom_path(size = 2, linejoin = "round", lineend = "round") +
  geom_point(size = 3) +
  coord_cartesian(xlim = c(0, 10), ylim = c(0, 10)) +
  labs(x = "X", y = "y") +
  theme_bw()

plot2 <- ggplot(drop_na(tornado, dy), aes(x = dy, y = y)) +
  geom_vline(xintercept = 0, size = 1, linetype = "dotted") +
  geom_path(size = 2, linejoin = "round", lineend = "round") +
  geom_point(size = 3) +
  coord_cartesian(xlim = c(-2, 2), ylim = c(0, 10)) +
  annotate(geom = "text", x = -Inf, y = 0, 
           label = "← y value decreasing",
           hjust = -0.1, fontface = "bold") +
  annotate(geom = "text", x = Inf, y = 0, 
           label = "y value increasing →",
           hjust = 1.1, fontface = "bold") +
  labs(x = "Change in y", y = "y") +
  theme_bw()

plot1 + plot2