vector1<-seq(from=2, to=50, by=2)
vector1[20]

## [1] 40

vector1[c(10,15,20)]

## [1] 20 30 40

vector1[10:20]

##  [1] 20 22 24 26 28 30 32 34 36 38 40

vector1[vector1>40]

## [1] 42 44 46 48 50

##自己练习写

vec <- c(3, 7, 2, 9, 4, 6)
new_vec <- vec[vec > 5]
print(new_vec)

## [1] 7 9 6

df <- data.frame(name = c("Alice", "Bob", "Charlie", "David"),age = c(25, 35, 40, 28))
new_df <- df[df$age > 30, ]
print(new_df)

##      name age
## 2     Bob  35
## 3 Charlie  40

new_df_subset <- subset(df, age > 30)
print(new_df_subset)

##      name age
## 2     Bob  35
## 3 Charlie  40

df_scores <- data.frame(score1 = c(75, 85, 90, 70),score2 = c(65, 75, 80, 60))
result <- df_scores[(df_scores$score1 > 80) & (df_scores$score2 > 70), ]
print(result)

##   score1 score2
## 2     85     75
## 3     90     80