R snippet: generate exaple trend data and fit loess smooth

snippet_trend_generate_smooth.r

library(dplyr)
library(ggplot2)

set.seed(1234)
d.trend <- data.frame(
  year = seq(as.Date("1911/1/1"), as.Date("2010/1/1"), "years"),
  female = seq(1,100)*runif(100,0,1),
  male = seq(1,100)*runif(100,0,1))
d.trend$total = d.trend$male + d.trend$female
  
d.trend <- d.trend %>%
  gather(gender, employed, male, female, total)

p.trend <- ggplot(d.trend, aes(
  x = year, y = employed,
  group = gender, color = gender))
p.trend <- p.trend + xlim(c(as.Date("1911/1/1"), as.Date("2020/1/1")))
p.trend <- p.trend + geom_point() + stat_smooth(method='lm', fullrange = TRUE)
p.trend