从不平衡到平衡面板 [英] From Unbalanced to Balanced Panel

问题描述

我可以在一个组内填充缺少的行，其中一个组由特定的（id1，id2）定义。

I wand to fill in missing rows within a group, where a group is defined by a specific (id1,id2).

例如我有一个数据集

  id1   id2  year  value
  33    29  1990     3.5
  33    29  1993     3.3
  33    29  1994     3.1
  32    28  1992     3.1
  32    28  1993     4.5

以获取以下数据集

 id1   id2  year   value
  33    29  1990     3.5
  33    29  1991      NA
  33    29  1992      NA
  33    29  1993     3.3
  33    29  1994     3.1
  32    28  1992     3.1
  32    28  1993     4.5

请注意，不需要创建 year == 1991，year == 1992 为第二组。示例是简化的，但是解决方案应该适用于字符串/数字，以及几个值列而不是一个。

Note that row with year==1991,year==1992 does not need to be created for the second group. The example is simplified, but the solution should work for strings/numerics, and for several value columns instead of just one.

推荐答案

如何？

require(data.table)
DT = data.table(id1 = c(33,33,33,32,32),
                id2 = c(29,29,29,28,28),  
               year = c(1990,1993,1994,1991,1992),
              value = c(3.5,3.3,3.1,3.1,4.5))


setkey(DT, id1,id2,year)
ans = DT[, list(year = seq.int(year[1L], year[.N])), by = list(id1,id2)]
ans = DT[setkey(ans)]
#    id1 id2 year value
# 1:  32  28 1991   3.1
# 2:  32  28 1992   4.5
# 3:  33  29 1990   3.5
# 4:  33  29 1991    NA
# 5:  33  29 1992    NA
# 6:  33  29 1993   3.3
# 7:  33  29 1994   3.1

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