R Notebook

if("dplyr" %in% installed.packages("dplyr") == FALSE)install.packages("dplyr")
library(dplyr)
exam <- read.csv("https://www.dropbox.com/s/z7si9jpm3n7wpo3/csv_exam.csv?dl=1")
head(exam)
class(exam)
exam %>% dplyr::filter(class == 1 | math > 50)
exam %>% dplyr::filter(class == 1 | class == 3 | class == 5)
exam %>% dplyr::filter(class %in% c(1,3,5))
class1 <- exam %>% dplyr::filter(class = 1)
mean(class1$math)
exam %>% select(-math)
# 1반의 수학점수를 내림차순으로 정렬하시오.
exam %>%
  filter(class==1) %>% 
  select(math) %>% 
  arrange(desc(math))

exam %>% 
  arrange(class, desc(math)) %>% 
  mutate(total = math+english+science) %>% 
  head