有条件地创建数据行

Question

示例数据集：

Price=c(6651, 7255, 25465, 35645, 2556, 3665)
NumberPurchased=c(25, 30, 156, 250, 12, 16)
Type=c("A", "A", "C", "C", "B", "B")
Source=c("GSC", "MYL", "TTC", "ZAF", "CAN", "HLT")
df1 <- data.frame(Price, NumberPurchased, Type, Source)

我希望能够使用两个附加变量（ID、PurchaseDate）创建一个新的数据框，但基于变量 Type 的数据行更多。

我要应用的规则：如果 Type=A，则 PurchaseDate 为“2013”、“2014”。如果 Type=B，则 PurchaseDate 为“2013”。如果 Type=C，PurchaseDate 为“2013”、“2014”、“2015”。

如果Type是A，将Price和NumberPurchased除以2，得到2行不同的PurchaseDate，如上所述。如果 Type 是 B，则 PurhcaseDate 保留为 2013。如果 Type 是 C，将 Price 和 NumberPurchased 除以 3，并有 3 行不同的 PurchaseDate 如上所述。

因此，我想要这样的东西作为新数据集：

Price=c(3325.5, 3325.5, 3627.5, 3627.5, 8488.3, 8488.3, 8488.3, 11881.6, 11881.6, 11881.6, 2556, 3665)
NumberPurchased=c(12.5, 12.5, 15, 15, 52, 52, 52, 83.3, 83.3, 83.3, 12, 16)
Type=c("A", "A", "A", "A", "C", "C", "C", "C", "C", "C","B", "B")
Source=c("GSC", "GSC", "MYL", "MYL", "TTC","TTC", "TTC",  "ZAF", "ZAF","ZAF", "CAN", "HLT")
PurchaseDate=c("2013", "2014", "2013", "2014", "2013", "2014", "2015", "2013", "2014", "2015", "2013", "2013")
ID=c(1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 5, 6)
df2 <- data.frame(Price, NumberPurchased, Type, Source, PurchaseDate, ID)

有什么见解吗？

Answer 1

这是一种可能的方法。首先，我们将为 Type 创建一个索引，然后我们将相应地增长数据，然后我们将使用 data.table 包来计算新变量。

library(data.table)
setDT(df1)[, indx := as.numeric(factor(Type, levels = c("B", "A", "C")))]
# setDT(df1)[, indx := ifelse(Type == "C", 3, 2)] # Alternative index per your comment
df2 <- df1[rep(seq_len(.N), indx)]

df2[, `:=`(
            Price = Price/.N,
            PurchaseDate = 2013:(2013 + (.N - 1)),
            NumberPurchased = NumberPurchased/.N,
            ID = .GRP
           ), 
           by = .(Source, Type)][]

#         Price NumberPurchased Type Source indx PurchaseDate ID
#  1:  3325.500        12.50000    A    GSC    2         2013  1
#  2:  3325.500        12.50000    A    GSC    2         2014  1
#  3:  3627.500        15.00000    A    MYL    2         2013  2
#  4:  3627.500        15.00000    A    MYL    2         2014  2
#  5:  8488.333        52.00000    C    TTC    3         2013  3
#  6:  8488.333        52.00000    C    TTC    3         2014  3
#  7:  8488.333        52.00000    C    TTC    3         2015  3
#  8: 11881.667        83.33333    C    ZAF    3         2013  4
#  9: 11881.667        83.33333    C    ZAF    3         2014  4
# 10: 11881.667        83.33333    C    ZAF    3         2015  4
# 11:  2556.000        12.00000    B    CAN    1         2013  5
# 12:  3665.000        16.00000    B    HLT    1         2013  6

有条件地创建数据行

Create rows of data conditionally

r

conditional-statements