相关疑难解决方法(0)

给出两个数据框:

df1 = data.frame(CustomerId = c(1:6), Product = c(rep("Toaster", 3), rep("Radio", 3)))
df2 = data.frame(CustomerId = c(2, 4, 6), State = c(rep("Alabama", 2), rep("Ohio", 1)))

df1
#  CustomerId Product
#           1 Toaster
#           2 Toaster
#           3 Toaster
#           4   Radio
#           5   Radio
#           6   Radio

df2
#  CustomerId   State
#           2 Alabama
#           4 Alabama
#           6    Ohio

我怎样才能做数据库风格,即sql风格,加入？也就是说,我该怎么做:

• 一个内连接的df1和df2:
  只返回行中左表在右表匹配的密钥.
• 一个外连接的df1和df2:
  返回两个表中的所有行,从有右表中的匹配键左连接记录.
• 甲 …

我有一个带有数以千计的代码的df,用于不同的未来合约.它们有缩写名称(稍后出现)和长名称(我希望在其他df中有)

full_list <- structure(
  list(
    Ticker = c("AC", "AIC", "BBS", "BO", "C", "DF"),
    Long_Name = c("Ethanol -- CBOT", "DJ UBS Commodity Index -- CBOT", "South American Soybeans -- CBOT", "Soybean Oil -- CBT", "Corn -- CBT", "Dow Jones Industrial Average -- CBT")
  ),
  .Names = c("Ticker", "Long_Name"),
  row.names = c(NA, 6L),
  class = "data.frame"
)

这个df有我每天收到的列表.我必须去查找缩写名称并将其与长名称匹配.

replace <- structure(
  list(
    Type = c("F", "F", "F", "F", "F", "F"),
    Location = c("US", "US", "US", "US", "US", "US"),
    Symbol = c("BO", "C", …

pandas.merge_asof 合并两个数据帧，执行左连接，除非它匹配最近的键而不是相等的键。

示例（从文档中窃取）：

>>> quotes
                     time ticker     bid     ask
0 2016-05-25 13:30:00.023   GOOG  720.50  720.93
1 2016-05-25 13:30:00.023   MSFT   51.95   51.96
2 2016-05-25 13:30:00.030   MSFT   51.97   51.98
3 2016-05-25 13:30:00.041   MSFT   51.99   52.00
4 2016-05-25 13:30:00.048   GOOG  720.50  720.93
5 2016-05-25 13:30:00.049   AAPL   97.99   98.01
6 2016-05-25 13:30:00.072   GOOG  720.50  720.88
7 2016-05-25 13:30:00.075   MSFT   52.01   52.03

>>> trades
                     time ticker   price  quantity
0 2016-05-25 13:30:00.023   MSFT   51.95        75
1 2016-05-25 13:30:00.038   MSFT   51.95       155
2 2016-05-25 13:30:00.048 …