x <- 1:30 
y <- seq(1, 300, 10) + rnorm(30) 
y[5] <- y[5] + 10
y[10] <- y[10] + 5
y[25] <- y[25] - 10
fit <- lm(y ~ x)
plot(fit)

y[15] <- y[15] + 15
y[20] <- y[20] + 10
y[25] <- y[25] - 5
fit <- lm(y ~ x)
plot(fit)

y[15] <- y[15] + 40
y[20] <- y[20] + 50
y[25] <- y[25] - 30
fit <- lm(y ~ x)
plot(fit)

y[10] <- y[10] + 10
y[15] <- y[15] + 5
y[30] <- y[30] - 10
fit <- lm(y ~ x)
plot(fit)

y[15] <- y[15] + 10
y[20] <- y[20] + 15
y[25] <- y[25] - 20
fit <- lm(y ~ x)
plot(fit)