# 데이터셋
data()
iris
str(iris)
View(iris)
edit(iris)
mpg
str(mpg)
dim(mpg)
colnames(mpg)
#grep함수로 추출 : 시작 ^a, 끝 a$
mpg
colnames(mpg)
#a문자를 포함하는 변수명 추출
grep("a", colnames(mpg))
mpg[ , grep("a", colnames(mpg)) ]
#substr함수
colnames(mpg)
substr( colnames(mpg), start=1, stop =2)
substr( colnames(mpg), start=1, stop =2) == 'cl'
mpg[ , substr( colnames(mpg), start=1, stop =2) == 'cl']
# 행추출
colnames(mpg)
mpg$class
mpg$class == "suv"
mpg[ mpg$class == "suv", ]
mpg$year >= 2007
mpg[ mpg$year >= 2007 , ]
(mpg$class == "compact") & (mpg$year >= 2007)
mpg[ (mpg$class == "compact") & (mpg$year >= 2007) , ]
mpg[ (mpg$class == "compact") | (mpg$year >= 2007) , ]