add web material

web/2_a

+new_mpg <- read_csv(
+  "http://perso.ens-lyon.fr/laurent.modolo/R/2_data.csv"
+)
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web/2_b

+ggplot(data = new_mpg) + 
+  geom_point(mapping = aes(x = displ, y = hwy))
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web/2_d

+ggplot(data = mpg, mapping = aes(x = displ, y = hwy, color = drv)) + 
+  geom_point() + 
+  geom_smooth(se = FALSE)
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