Question

我有以下数据框，包括餐馆（id＃），所有者和购买日期。有时餐厅会更改所有权，但出于分析目的，我想创建另一个列，该列仅保留最新所有者的名称，这由“购买日期”确定。我该如何创建这个新专栏？在此示例中，餐厅23在2013年1月1日进行了更改，因此我想仅包括新所有者的名称（Bob）作为此餐厅所有行的当前所有者，如下所示。如果餐厅没有转手，请将“当前所有者”列保留为与“所有者”列相同的名称。

    Restaurant <- c(23,23,23,23,23,23,23,15,15,15,15,17,17,17,17)

    owner <- c("Chuck","Chuck","Chuck","Chuck","Bob","Bob","Bob",
    "Hazel","Hazel","Hazel","Hazel","Pete","Pete","Pete","Pete")

    purchaseDate <- c("3/4/2011","3/4/2011","3/4/2011","3/4/2011",
    "1/1/2013","1/1/2013","1/1/2013","4/11/2010","4/11/2010","4/11/2010",
    "4/11/2010","9/2/2012","9/2/2012","9/2/2012","9/2/2012")

    df <- data.frame( Restaurant = Restaurant, owner=owner, purchaseDate=purchaseDate)

    df$currentOwner <- c("Bob","Bob","Bob","Bob","Bob","Bob","Bob","Hazel","Hazel","Hazel","Hazel","Pete","Pete","Pete","Pete")

Answer 1

您可以使用：

do.call(rbind, by(df, df$Restaurant, function(d)
        within(d, currentOwner2 <- as.character(
            owner[which.max(as.Date(purchaseDate, format="%d/%m/%Y"))]))))

感谢@Thomas挖掘这个问题： - ）

根据多列中的值在R数据框中创建新列

1 个答案: