# install.packages(c("readxl","ggplot2","dplyr"))

library(readxl)

library(ggplot2)

library(dplyr)

문제 1

library(ggplot2)

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

mpg[c(10,14,58, 93), "drv"] <- "k"

mpg[c(29, 43, 129, 203), "cty"] <- c(3,4,39, 42)

Including Plots

You can also embed plots, for example:

table(mpg$drv)
## 
##   4   f   k   r 
## 100 106   4  24

library(dplyr)

mpg$drv <- ifelse(mpg$drv %in% c("4","f","r"), mpg$drv, NA)

table(mpg$drv)
## 
##   4   f   r 
## 100 106  24

문제 2

boxplot(mpg$cty)

boxplot(mpg$cty)$stats

##      [,1]
## [1,]    9
## [2,]   14
## [3,]   17
## [4,]   19
## [5,]   26

값을 볼 수 있게 더해주기

9에서 26 사이 아니면 이상 값

mpg$cty <- ifelse(mpg$cty <9 | mpg$cty >26, NA, mpg$cty)

boxplot(mpg$cty)

##문제 3

library(dplyr)

mpg %>% 

  filter(!is.na(drv) & !is.na(cty)) %>% 

  group_by(drv) %>% 

  summarise(mean_cty = mean(cty))
## # A tibble: 3 × 2
##   drv   mean_cty
##   <chr>    <dbl>
## 1 4         14.2
## 2 f         19.5
## 3 r         14.0