Hi, folks,

Please let me address the problem by the following codes:

first=c('u','b','e','k','j','c','u','f','c','e')
second=c('usa','Brazil','England','Korea','Japan','China','usa','France','China','England')
third=1:10
data=data.frame(first,second,third)

## You may understand values in the first column are the unique codes for
those in the second column.
####So 'u' is only for usa. Replicate values appear the same rows for the
first and second columns.
### Now I want to delete replicate rows with the same values in first
(sceond) rows
####and sum up values in the third column for the same values.

mm=melt(data,id='first')
sum=cast(mm,first~variable,sum)

### This does not work. ><

But the expected dataframe is like this:

1      u    third     8
2      b    third     2
3      e    third     13
4      k    third     4
5      j    third     5
6      c    third     15
8      f    third     8
Thanks in advance.

Yi

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