Question

I have to merge to data frames in R. The two data frames share a common id variable, the name of the subject. However, the names in one data frame are partly capitalized, while in the other they are in lower cases. Furthermore the names appear in reverse order. Here is a sample from the data frames:

DataFrame1$Name:
"Van Brempt Kathleen"
"Gräßle Ingeborg"
"Gauzès Jean-Paul"
"Winkler Iuliu" 

DataFrame2$Name:
"Kathleen VAN BREMPT" 
"Ingeborg GRÄSSLE"
"Jean-Paul GAUZÈS"
"Iuliu WINKLER"

Is there a way in R to make these two variables usable as an identifier for merging the data frames?

Best, Thomas

Answer 1

Here’s a complete solution that combines the two partial methods offered so far (and overcomes the fears expressed by Spacedman about “matching Grassle with Graßle”):

DataFrame2$revname <- gsub("([^\\s]*)\\s(.*)","\\2 \\1",DataFrame2$Name,perl=TRUE)
DataFrame2$agnum <-sapply(tolower(DataFrame2$revname), agrep, tolower(DataFrame1$Name) )
DataFrame1$num <-1:nrow(DataFrame1)
merge(DataFrame1, DataFrame2, by.x="num", by.y="agnum")

Output:

  num              Name.x              Name.y             revname

1   1 Van Brempt Kathleen Kathleen VAN BREMPT VAN BREMPT Kathleen
2   2     Gräßle Ingeborg    Ingeborg GRÄSSLE    GRÄSSLE Ingeborg
3   3    Gauzès Jean-Paul    Jean-Paul GAUZÈS    GAUZÈS Jean-Paul
4   4       Winkler Iuliu       Iuliu WINKLER       WINKLER Iuliu

The third step would not be necessary if DatFrame1 had rownames that were still sequentially numbered (as they would be by default). The merge statement would then be:

merge(DataFrame1, DataFrame2, by.x="row.names", by.y="agnum")

—
David.