example.R

library(tidyverse)

n <- 200
step <- 0.02
sm_step <- 0.02
v <- 10

tmp <- data_frame(x = 1:200,
                  a = x * 0 + rnorm(n, 0, v),
                  b = x * (0 - step - 1 * sm_step) + rnorm(n, 0, v) + (step + 1 * sm_step) * 100,
                  c = x * (0 - step - 2 * sm_step) + rnorm(n, 0, v) + (step + 2 * sm_step) * 100,
                  d = x * (0 - step - 3 * sm_step) + rnorm(n, 0, v) + (step + 3 * sm_step) * 100,
                  e = x * (0 - step - 4 * sm_step) + rnorm(n, 0, v) + (step + 4 * sm_step) * 100)

tmp2 <- gather(tmp, var, val, -x)

ggplot(tmp2, aes(x, val, col = var)) + geom_point()

fm <- lm(val ~ x * var, tmp2)
summary(fm)
tmp3 <- cbind(tmp2, predict(fm, interval = 'confidence'))

ggplot(tmp3, aes(x, fit, ymin = lwr, ymax = upr, col = var, fill = var)) + 
  geom_line() +
  geom_ribbon(alpha = 0.3, col = NA) +
  theme_bw()