r - 从 R 中的多个列表对象中提取相同字段的值

Question

我有一个列表对象如下:

structure(list(bga_u = structure(list(buy_target_price = numeric(0), 
    sell_target_price = numeric(0), units_holding = 0, tx_record = structure(list(
        `2010-12-01` = structure(list(buy_date = structure(14944, class = "Date"), 
            offer_price = 40.58, buy_unit = 3.15931809278285, 
            status = "hold"), .Names = c("buy_date", "offer_price", 
        "buy_unit", "status")), `2011-01-03` = structure(list(
            buy_date = structure(14977, class = "Date"), offer_price = 42.2, 
            buy_unit = 3.03803621339166, status = "hold"), .Names = c("buy_date", 
        "offer_price", "buy_unit", "status")), `2011-02-01` = structure(list(
            buy_date = structure(15006, class = "Date"), offer_price = 42.59, 
            buy_unit = 3.01021667539629, status = "hold"), .Names = c("buy_date", 
        "offer_price", "buy_unit", "status")), `2011-03-01` = structure(list(
            buy_date = structure(15034, class = "Date"), offer_price = 43.37, 
            buy_unit = 2.95607858439309, status = "hold"), .Names = c("buy_date", 
        "offer_price", "buy_unit", "status")), `2011-04-01` = structure(list(
            buy_date = structure(15065, class = "Date"), offer_price = 43.35, 
            buy_unit = 2.95744240380919, status = "hold"), .Names = c("buy_date", 
        "offer_price", "buy_unit", "status")), `2011-05-03` = structure(list(
            buy_date = structure(15097, class = "Date"), offer_price = 44.53, 
            buy_unit = 2.87907316876551, status = "hold"), .Names = c("buy_date", 
        "offer_price", "buy_unit", "status"))), .Names = c("2010-12-01", 
    "2011-01-03", "2011-02-01", "2011-03-01", "2011-04-01", "2011-05-03"
    ))), .Names = c("buy_target_price", "sell_target_price", 
"units_holding", "tx_record")), bwg_u = structure(list(buy_target_price = numeric(0), 
    sell_target_price = numeric(0), units_holding = 0, tx_record = structure(list(
        `2010-11-02` = structure(list(buy_date = structure(14915, class = "Date"), 
            offer_price = 63.15, buy_unit = 2.03016830095215, 
            status = "hold"), .Names = c("buy_date", "offer_price", 
        "buy_unit", "status")), `2010-12-01` = structure(list(
            buy_date = structure(14944, class = "Date"), offer_price = 64.19, 
            buy_unit = 1.99727571592348, status = "hold"), .Names = c("buy_date", 
        "offer_price", "buy_unit", "status")), `2011-09-01` = structure(list(
            buy_date = structure(15218, class = "Date"), offer_price = 69.29, 
            buy_unit = 1.85026884406304, status = "hold"), .Names = c("buy_date", 
        "offer_price", "buy_unit", "status")), `2011-10-03` = structure(list(
            buy_date = structure(15250, class = "Date"), offer_price = 58.05, 
            buy_unit = 2.20852934031229, status = "hold"), .Names = c("buy_date", 
        "offer_price", "buy_unit", "status"))), .Names = c("2010-11-02", 
    "2010-12-01", "2011-09-01", "2011-10-03"))), .Names = c("buy_target_price", 
"sell_target_price", "units_holding", "tx_record"))), .Names = c("bga_u", 
"bwg_u"))

这是一个“列表中的列表”对象，由 3 个级别组成:

第 1 级:所有基金的名称(此处有 2 个基金:bga _u 和 bwg_u)

级别 2:目标买入价；目标卖出价；和单位控股

级别 3:特定交易的详细信息(例如购买的单位)

如果该特定交易的状态仍为“持有”，则存储在级别 2 中的“持有单位”是通过将级别 3 中每笔交易的“买入单位”相加来计算的。

如何计算每只基金的“单位持有量”并放入第 2 级？

(我使用 R 2-3 年，但我是 list 对象的新手，我可能在概念上对 list 有误。)

Answer 1

这是一种方法(假设对象是名称 dat ):

lapply(dat, function(x) 
  "[[<-"(x, "units_holding", 
         sum(sapply(x[["tx_record"]], function(y) 
           ifelse(y[["status"]] == "hold", y[["buy_unit"]], 0)))))

在这个命令中， lapply和 sapply分别用于迭代列表的第一级和第二级。

笔记。这会创建一个新对象，您可能希望将其分配给新变量(或覆盖旧变量)。