如何用R删除少数据的重复行？

Question

比方说，我有以下的数据表（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 

我想删除重复的行。如果我做data <- unique(data, by = NULL)，那么只有最后一行（第7行）被删除，但是我想删除第2行。我可以setkey()定义键：

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

，它会删除任何一列2或第3行，但我想删除行，它具有较少的数据，并保持与行更多的数据。即在上面的情况下，第2行应该被删除，但第3行应该保留，因为它在第company列中具有附加值。我该怎么做？

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]