合並列名上的 2、1 行 data.tables

Question

我有 2、1 行 data.tables。

dt1 <- data.table(a = 0, b = 0, c = 0)
dt2 <- data.table(a = 1, c = 5)

我的目標是用dt2的值更新dt1以便我得到：

desired_dt <- data.table(a = 1, b = 0, c = 5) 

我嘗試合並，假設它與共享列名匹配，但沒有運氣。

dt2[dt1]

Error in `[.data.table`(dt2, dt1) : 
When i is a data.table (or character vector), the columns to join by must be specified using 'on=' 
argument (see ?data.table), by keying x (i.e. sorted, and, marked as sorted, see ?setkey), or by 
sharing column names between x and i (i.e., a natural join). Keyed joins might have further speed 
benefits on very large data due to x being sorted in RAM.

這不被認為是自然加入嗎？ 對於我所缺少的東西，我將不勝感激！

Answer 1

我們得到intersect的列名並進行賦值

nm1 <- intersect(names(dt1), names(dt2))
dt1[, (nm1) := dt2]

---

或者我們可以set密鑰

setkeyv(dt1, intersect(names(dt1), names(dt2)))
out <- dt1[dt2]
for(j in seq_along(out)) set(out, i = which(is.na(out[[j]])), j=j, value = 0)

Answer 2

這是使用rbindlist + fcoalesce的data.table選項

setcolorder(
  rbindlist(
    list(dt2, dt1),
    fill = TRUE
  )[
    ,
    lapply(.SD, function(x) fcoalesce(as.list(x)))
  ], names(dt1)
)[]

這使

   a b c
1: 1 0 5