Unknown college 14 days punch notes Day2

num1<-c(9.1,8.2,7.3)
num2<-1:10
char<-c('a','b','c')
logit<-c(TRUE,FALSE,T,F)
c(1,'a',TRUE)
sex<-c('F','M','F','M')
sexf<-factor(sex)

num1[1]
num1[c(1,3)]
num1[c(T,F,T)]
num1[-2]
num3<-c('first'=9.1,'second'=8.2,'third'=7.3)
num3[c('first','third')]

 

#1
a<-1:100
a
#2
a[1]<-0
a
#3
a[-(1:20)]

#4
b<-1:100
b[b%%2==1]

#5