排序與子集化 factor

R for Finance 入門

Lore Dirick

Manager of Data Science Curriculum at Flatiron School

設定順序

第 4 章投影片 2 圖片

rank <- c("low", "medium", "low", "medium", "high")

rank_wrong_order <- ordered(rank)

rank_wrong_order

low    medium low    medium high  
Levels: high < low < medium

rank_order <- factor(rank, ordered = TRUE,
                     levels = c("low", "medium", "high"))
rank_order

low    medium low    medium high  
Levels: low < medium < high

summary(rank_order)

low medium   high 
  2      2      1

# Only low
rank_order[c(1,3)]

low low
Levels: low < medium < high

summary(rank_order[c(1,3)])

low medium   high 
  2      0      0

# Only low, drop medium and high levels
rank_order[c(1,3), drop = TRUE]

low low
Levels: low

summary(rank_order[c(1,3), drop = TRUE])

low 
  2

R for Finance 入門