Delete lab_2.R

lab_2.R

-
-# Lab 2
-# tidyverse
-
-# install packages
-install.packages("tidyverse")
-
-# load packages 
-library(tidyverse)
-require(tidyverse)
-
-
-# the pipe operator -- %>% 
-?mtcars
-mtcars
-
-sqrt(mean(colSums(mtcars)))
-mtcars %>% colSums %>% mean %>% sqrt
-
-# x %>% f()           f(x)
-# x %>% f %>% g     g(f(x))
-
-
-# select columns -- select()
-mtcars %>% select(mpg, cyl, hp)
-mtcars %>% select(-am, -vs)
-
-
-# select rows -- filter()
-mtcars %>% filter(cyl == 8)
-mtcars %>% filter(cyl == 8 & gear >= 5)
-
-
-# create columns -- mutate()
-mtcars %>% mutate(four_cyl = (cyl == 4), twice_hp = 2 * hp)
-
-
-# sort -- arrange()
-mtcars %>% arrange(vs)
-mtcars %>% arrange(vs, desc(gear))
-
-
-# exercise
-mtcars %>% 
-  select(-qsec) %>% 
-  filter(carb > 2) %>% 
-  mutate(twice_mpg = 2 * mpg) %>% 
-  arrange(hp, disp, desc(vs))
-
-
-# present basic statistics -- summarize()
-# by group -- group_by()
-mtcars %>% summarise(mean(hp), sum(mpg), min(gear), median(carb), count=n())
-mtcars %>% group_by(vs) %>% summarise(mean(hp), n())
-
-
-?group_by
-
-
-