如何用R刪除少數據的重複行？

Question

比方說，我有以下的數據表（如data）：

row,or,d,ddate,rdate,changes,class,price,fdate,company,number,minutes,added,source 
1,VA1,VA2,2014-05-24,,0,0,2124,2014-05-22 15:50:16,,,,2014-05-22 12:20:03,tp 
2,VA1,VA2,2014-05-26,,0,0,2124,2014-05-22 15:03:44,,,,2014-05-22 12:20:03,tp 
3,VA1,VA2,2014-05-26,,0,0,2124,2014-05-22 15:03:44,A1,,,2014-05-22 12:20:03,tp 
4,VA1,VA2,2014-06-05,,0,0,2124,2014-05-22 15:48:24,,,,2014-05-22 12:20:03,tp 
5,VA1,VA2,2014-06-09,,0,0,2124,2014-05-22 15:37:35,,,,2014-05-22 12:20:03,tp 
6,VA1,VA2,2014-06-16,,0,0,2124,2014-05-22 14:17:33,,,,2014-05-22 12:20:03,tp 
7,VA1,VA2,2014-06-16,,0,0,2124,2014-05-22 14:17:33,,,,2014-05-22 12:20:03,tp 

我想刪除重複的行。如果我做data <- unique(data, by = NULL)，那麼只有最後一行（第7行）被刪除，但是我想刪除第2行。我可以setkey()定義鍵：

setkey(data, row,or,d,ddate,rdate,changes,class,price,fdate,number,minutes,added,source) 

，它會刪除任何一列2或第3行，但我想刪除行，它具有較少的數據，並保持與行更多的數據。即在上面的情況下，第2行應該被刪除，但第3行應該保留，因爲它在第company列中具有附加值。我該怎麼做？

Answer 1

如何：

# whatever the important columns are for your uniqueness criterion 
important.cols = c('or','d','ddate','rdate','changes','class','price','fdate') 

# pick row with max number of non-empty elements 
dt[, .SD[which.max(rowSums(.SD != "", na.rm = T))], by = important.cols]