[英]Merging two data.tables while doing running sum in R
I have a data.table which represents the dividend payed by a company from 2019 to 2021.我有一个 data.table,它代表了一家公司从 2019 年到 2021 年支付的股息。
library(data.table)
div_dt <- structure(list(pay_date = structure(c(18885L, 18793L, 18701L,
18611L, 18520L, 18428L, 18337L, 18246L, 18155L, 18064L, 17910L
), class = c("IDate", "Date")), cash_amount = c(0.09, 0.09, 0.09,
0.09, 0.08, 0.07, 0.07, 0.05, 0.04, 0.04, 0.07)), row.names = c(NA,
-11L), class = c("data.table", "data.frame"))
Below is a table showing all calendar days of this stock between 2019 to 2021.下表显示了该股票在 2019 年至 2021 年之间的所有日历日。
calendar_dt = data.table(current_date = seq(min(div_dt$pay_date), max(div_dt$pay_date), by="days"))
I want to show the sum of the last 4 quarters of dividends this stock has paid on any given date.我想显示该股票在任何给定日期支付的过去 4 个季度的股息总和。 To solve this I have added a new column
div_start_date
to calendar_dt
, which shows the start date form which dividend has to be added to the given date current_date
.为了解决这个问题,我在
calendar_dt
添加了一个新列div_start_date
,它显示了必须将股息添加到给定日期current_date
的开始日期形式。
calendar_dt[, div_start_date := date - 365]
Can someone show me how to merge these tables so that for each calendar day in calendar_dt
, the sum of dividends of the past 4 quarters is shown in a new column?有人可以告诉我如何合并这些表,以便在
calendar_dt
每个日历日,过去 4 个季度的股息总和显示在新列中吗?
this will work (not the most efficient join, but willl get the job done)这会起作用(不是最有效的加入,但会完成工作)
# set keys
setkey(calendar_dt, current_date)
setkey(div_dt, pay_date)
# join
calendar_dt[calendar_dt,
cast_last_365 := div_dt[pay_date %between% c(current_date - 365, current_date),
sum(cash_amount)],
by = .EACHI]
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