R 中的购物篮分析
Christopher Bruffaerts
Statistician
交易（Transaction）：买卖某物的行为。
交易数据（Transactional data）： 某位顾客在一次购买中买到的全部商品列表。
单笔交易示例：
TID Product 1 1 Bread 2 1 Cheese 3 1 Cheese 4 1 Cheese
Transactions 类： 表示用于挖掘项集或规则的交易数据。
可由以下强制转换：
但需先准备好数据。
处理交易数据时要点
用于标识产品的字段/列
用于标识交易的字段/列
门店的交易数据
my_transactions = data.frame( "TID" = c(1,1,1,1, 2,2,2, 3,3, 4,4,4, 5,5, 6,6, 7,7), "Product" = c("Bread", "Cheese", "Cheese", "Cheese", "Bread", "Butter", "Wine", "Butter", "Butter", "Butter", "Wine", "Wine", "Butter", "Cheese", "Cheese", "Wine", "Wine", "Wine") )
交易一瞥
head(my_transactions, 10)
TID Product 1 1 Bread 2 1 Butter 3 1 Cheese 4 1 Wine 5 2 Bread 6 2 Butter 7 2 Wine 8 3 Bread 9 3 Butter 10 4 Butter
用 split 函数创建列表
# 将 TID 转为因子 my_transactions$TID = factor(my_transactions$TID) # 按组拆分 data_list = split(my_transactions$Product, my_transactions$TID)
data_list
$`1` [1] Bread Butter Cheese Wine Levels: Bread Butter Cheese Wine $`2` [1] Bread Butter Wine Levels: Bread Butter Cheese Wine $`3` [1] Bread Butter Levels: Bread Butter Cheese Wine
转换为 transaction 类
# 转为交易数据集 data_trx = as(data_list,"transactions") # 查看交易 inspect(data_trx)
交易数据预览
items transactionID [1] {Bread,Butter,Cheese,Wine} 1 [2] {Bread,Butter,Wine} 2 [3] {Bread,Butter} 3 [4] {Butter,Cheese,Wine} 4 [5] {Butter,Cheese} 5 [6] {Cheese,Wine} 6 [7] {Butter,Wine} 7
交易概览
inspect(head(data_trx))
items transactionID [1] {Bread,Butter,Cheese,Wine} 1 [2] {Bread,Butter,Wine} 2 [3] {Bread,Butter} 3 [4] {Butter,Cheese,Wine} 4 [5] {Butter,Cheese} 5 [6] {Cheese,Wine} 6
访问特定交易
inspect(data_trx[1]) inspect(data_trx[1:3])
交易对象摘要
summary(data_trx)
绘制 ItemMatrix
image(data_trx)
警告：仅对少量交易使用该函数
有助于识别：
密度 = 18/28 = 0.64
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