P.133 혼자서해보기

혼자서해보기 Q1.

library(dplyr)

## 
## Attaching package: 'dplyr'

## The following objects are masked from 'package:stats':
## 
##     filter, lag

## The following objects are masked from 'package:base':
## 
##     intersect, setdiff, setequal, union

mpg <- as.data.frame(ggplot2::mpg)

mpg %>% filter(displ<=4) ->mpg_a
mpg %>% filter(displ >=5)->mpg_b

mean(mpg_a$hwy)

## [1] 25.96319

mean(mpg_b$hwy)

## [1] 18.07895

displ이 4 이하인 자동차의 hwy가 평균적으로 더 높다.

Q2

mpg %>% filter(manufacturer == "audi") -> mpg_audi
mpg %>% filter(manufacturer == "toyota") -> mpg_toyota

mean(mpg_audi$cty)

## [1] 17.61111

mean(mpg_toyota$cty)

## [1] 18.52941

toyota의 cty가 평균적으로 더 높다.

Q3

mpg %>% filter(manufacturer %in% c("chevrolet", "ford","honda"))-> mpg_cfh

mean(mpg_cfh$hwy)

## [1] 22.50943