plotting the sketch: regional background + urban background + hotspots concentration

plot.R

# libraries
library(ggplot2)
library(dplyr)

# where is the urban area?
urban <- c(rep(F,100),rep(T,100),rep(F,100))

# regional background concentrations
noise <- runif(300,min=5, max = 15)
regional.background <- stats::filter(noise,rep(1/40,40), sides=2, circular = T)
regional.background <- stats::filter(regional.background,rep(1/40,40), sides=2, circular = T)
regional.background <- stats::filter(regional.background,rep(1/40,40), sides=2, circular = T)

# urban background
noise <- runif(300,min=2, max = 10)*urban
urban.background <- stats::filter(noise,rep(1/20,20), sides=2, circular = T)
urban.background <- stats::filter(urban.background,rep(1/20,20), sides=2, circular = T)

# concentration in the local hotspots
noise <- runif(300,min=-10, max = 10)*urban
hotspot <- stats::filter(noise,rep(1/3,3), sides=2, circular = T)
hotspot <- stats::filter(hotspot,rep(1/3,3), sides=2, circular = T)
hotspot <- as.ts(pmax(0,hotspot))

# the data frame
df <- bind_rows(data.frame(concentration=regional.background,
                           contribution="regional background",
                           x=1:300),
                data.frame(concentration=urban.background,
                           contribution="urban background",
                           x=1:300),
                data.frame(concentration=hotspot,
                           contribution="hotspot",
                           x=1:300))
df$contribution <- ordered(df$contribution, c("hotspot",
                                              "urban background",
                                              "regional background"))

# plotting
p <- ggplot(df, aes(x=x, y=concentration)) + 
  geom_area(aes(colour = contribution, fill= contribution), 
            position = 'stack', alpha=0.7) +
  scale_color_manual("",values=c("sienna","navyblue","olivedrab")) +
  scale_fill_manual("",values=c("sienna","navyblue","olivedrab")) +
  theme_classic() +
  scale_x_continuous(name="", breaks=c(50*(1:5)), 
                     labels=c("rural","","urban","","rural")) +
  theme(axis.ticks.x = element_line(color = c(NA,"black",NA,"black",NA)))

ggsave(p, filename = "reg-urb-loc.pdf", width = 7, height=4)