r - 如何更新data.table中的现有列值？

Question

我刚开始这个编程，很抱歉问这个简单的问题，但我被卡住了。

我有一个名为 s3 的 data.table:

s3:

ClaimID           dx      dxgroup
15nhbfcgcda       113.8   NA
15nhbfcgcda       156.8   NA
15nhbfcgcda       110.8   059
15nhbfcfssa       135.8   NA
15nhb4dfgda       V70.3   NA
15nhbf644da       118.8   042

S3 有 30000 行。

我想应用这个逻辑:

If dxgroup = NA(
    If dx (fisrt 4 characters match with)= (2024, 2967, 9786,9788,8263)
        then dxgroup = (first 4 character of dx)
    else dx (fisrt 3 characters match with) = (V70, 042,897)
        then dxgroup = (first 3 character of dx)
else dxgroup = dx
)

结果应该是这样的:

ClaimID           dx      dxgroup
15nhbfcgcda       113.8   113.8
15nhbfcgcda       156.8   156.8
15nhbfcgcda       110.8   059
15nhbfcfssa       135.8   135.8
15nhb4dfgda       V70.3   V70
15nhbf644da       118.8   042

请指教 ？

我道歉:这是我第一次在这里问问题，所以还不习惯。所以我做了这样的事情(如果这是正确的，我没有，我也有错误):

sample4<-sample3[, dxgroup := { if (dxgroup == NA)

• { if (substring(sample3$dx,1,4) == list (2501,2780,4151,5301,5751,6860,7807,7890,9898,9955,9970)) substring(sample3$dx,1,4)
• else if (substring(sample3$dx,1,3) == list (042,493,682,850,V72)) substring(sample3$dx,1,3)
• else if (substring(sample3$dx,1,4) == list (8540, 8541)) substring(sample3$dx,1,3)
• else if (substring(sample3$dx,1,3) == list (043, 044)) 042
• else if (substring(sample3$dx,1,3) == list (789) & substring(sample3$dx,1,3) != list(7891,7893,78930)) 7890
• else if (substring(sample3$dx,1,4) == list (7865) & substring(sample3$dx,1,4) != list(78651,78652,78659)) 78650}
• else sample3$dx}] Error in if (dxgroup == NA) { : missing value where TRUE/FALSE needed In addition: Warning message: In if (dxgroup == NA) { : the condition has length > 1 and only the first element will be used

Answer 1

你已经设置好了逻辑。

请注意，使用 data.table(嗯，几乎所有 R )，您可以包装 j在 {curly brackets}括号中的最后一个语句是将分配的内容。例如:

DT[,  dxgroup :=  { if (clause1)  
                     {if (foo) beebar else bar}
                  else chewybar
                  } 
  ]