I have two data frames, each with the same two columns: county codes and frequencies. They aren't identical, but some of the county code values show up in both data frames. Like this:
"county_code","freq"
"01011",2
"01051",1
"01073",9
"01077",1
"county_code","freq"
"01011",4
"01056",2
"01073",1
"01088",6
I want to merge them into a new data frame, such that if a county code appears in both data frames, their respective frequencies are added together. If the county code just appears in one or the other of the data frames, I want to add it (and its frequency) to the new data frame unchanged. The result should look like this:
"county_code","freq"
"01011",6
"01051",1
"01056",2
"01073",10
"01077",1
"01088",6
The result doesn't have to be ordered. I tried to use reshape for this, but I wasn't sure that was the right approach. Thoughts?
Combine the two data frames with rbind, then use aggregate to collapse multiple rows with the same county_code:
aggregate(freq~county_code, rbind(d1, d2) , FUN=sum)
## county_code freq
## 1 1011 6
## 2 1051 1
## 3 1073 10
## 4 1077 1
## 5 1056 2
## 6 1088 6
(Using the definitions in MrFlick's answer.)
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