220411

mpg1<-read.csv("mpg1.csv")
str(mpg1)

## 'data.frame':    234 obs. of  5 variables:
##  $ manufacturer: chr  "audi" "audi" "audi" "audi" ...
##  $ trans       : chr  "auto" "manual" "manual" "auto" ...
##  $ drv         : chr  "f" "f" "f" "f" ...
##  $ cty         : int  18 21 20 21 16 18 18 18 16 20 ...
##  $ hwy         : int  29 29 31 30 26 26 27 26 25 28 ...

table(mpg1$manufacturer)

## 
##       audi  chevrolet      dodge       ford      honda    hyundai       jeep 
##         18         19         37         25          9         14          8 
## land rover    lincoln    mercury     nissan    pontiac     subaru     toyota 
##          4          3          4         13          5         14         34 
## volkswagen 
##         27

b<-table(mpg1$trans,mpg1$drv)
str(b)

##  'table' int [1:2, 1:3] 75 28 65 41 17 8
##  - attr(*, "dimnames")=List of 2
##   ..$ : chr [1:2] "auto" "manual"
##   ..$ : chr [1:3] "4" "f" "r"

a<-table(mpg1$trans)
str(a)

##  'table' int [1:2(1d)] 157 77
##  - attr(*, "dimnames")=List of 1
##   ..$ : chr [1:2] "auto" "manual"

prop.table(a)

## 
##      auto    manual 
## 0.6709402 0.3290598

prop.table(b)

##         
##                   4          f          r
##   auto   0.32051282 0.27777778 0.07264957
##   manual 0.11965812 0.17521368 0.03418803

round(prop.table(a),2)

## 
##   auto manual 
##   0.67   0.33

summary(mpg1)

##  manufacturer          trans               drv                 cty       
##  Length:234         Length:234         Length:234         Min.   : 9.00  
##  Class :character   Class :character   Class :character   1st Qu.:14.00  
##  Mode  :character   Mode  :character   Mode  :character   Median :17.00  
##                                                           Mean   :16.86  
##                                                           3rd Qu.:19.00  
##                                                           Max.   :35.00  
##       hwy       
##  Min.   :12.00  
##  1st Qu.:18.00  
##  Median :24.00  
##  Mean   :23.44  
##  3rd Qu.:27.00  
##  Max.   :44.00

library(dplyr)

## 
## 다음의 패키지를 부착합니다: 'dplyr'

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

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

library(tidyverse)

## -- Attaching packages --------------------------------------- tidyverse 1.3.1 --

## v ggplot2 3.3.5     v purrr   0.3.4
## v tibble  3.1.6     v stringr 1.4.0
## v tidyr   1.1.4     v forcats 0.5.1
## v readr   2.1.0

## -- Conflicts ------------------------------------------ tidyverse_conflicts() --
## x dplyr::filter() masks stats::filter()
## x dplyr::lag()    masks stats::lag()

str(mpg1)

## 'data.frame':    234 obs. of  5 variables:
##  $ manufacturer: chr  "audi" "audi" "audi" "audi" ...
##  $ trans       : chr  "auto" "manual" "manual" "auto" ...
##  $ drv         : chr  "f" "f" "f" "f" ...
##  $ cty         : int  18 21 20 21 16 18 18 18 16 20 ...
##  $ hwy         : int  29 29 31 30 26 26 27 26 25 28 ...

mpg1_1<-mpg1 %>% rename(t=trans,m=manufacturer)
mpg1_2<-mpg1_1 %>% select(t,drv,cty)
head(mpg1_2)

##        t drv cty
## 1   auto   f  18
## 2 manual   f  21
## 3 manual   f  20
## 4   auto   f  21
## 5   auto   f  16
## 6 manual   f  18

mpg1_3<-mpg1 %>% filter(manufacturer=="audi"&trans=="auto"&drv=="f")
head(mpg1_3)

##   manufacturer trans drv cty hwy
## 1         audi  auto   f  18  29
## 2         audi  auto   f  21  30
## 3         audi  auto   f  16  26
## 4         audi  auto   f  18  27

str(mpg1_1)

## 'data.frame':    234 obs. of  5 variables:
##  $ m  : chr  "audi" "audi" "audi" "audi" ...
##  $ t  : chr  "auto" "manual" "manual" "auto" ...
##  $ drv: chr  "f" "f" "f" "f" ...
##  $ cty: int  18 21 20 21 16 18 18 18 16 20 ...
##  $ hwy: int  29 29 31 30 26 26 27 26 25 28 ...

str(mpg1_2)

## 'data.frame':    234 obs. of  3 variables:
##  $ t  : chr  "auto" "manual" "manual" "auto" ...
##  $ drv: chr  "f" "f" "f" "f" ...
##  $ cty: int  18 21 20 21 16 18 18 18 16 20 ...

str(mpg1_3)

## 'data.frame':    4 obs. of  5 variables:
##  $ manufacturer: chr  "audi" "audi" "audi" "audi"
##  $ trans       : chr  "auto" "auto" "auto" "auto"
##  $ drv         : chr  "f" "f" "f" "f"
##  $ cty         : int  18 21 16 18
##  $ hwy         : int  29 30 26 27

max(mpg1$cty)

## [1] 35