Question
I have 2 data frame that I want to compare. (I've already asked this question here, but am phrasing it differently to make it more efficient: How to find differences in elements of 2 data frames based on 2 unique identifiers)
https://stackoverflow.com/questions/19915784
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Russiandf1<-data.frame(DS.ID=c(123,214,543,325,123,214),OP.ID=c("xxab","xxac","xxad","xxae","xxaf","xxaq"),P.ID=c("AAC","JGK","DIF","ADL","AAC","JGR"),date="20121111")
> df1
DS.ID OP.ID P.ID date
1 123 xxab AAC 20121111
2 214 xxac JGK 20121111
3 543 xxad DIF 20121111
4 325 xxae ADL 20121111
5 123 xxaf AAC 20121111
6 214 xxaq JGR 20121111
df2<-data.frame(DS.ID=c(123,214,543,325,123,214),OP.ID=c("xxab","xxac","xxad","xxae","xxaf","xxaq"),P.ID=c("AAC","JGK","DIF","ADL","AAC","JGS"),date="20121110")
> df2
DS.ID OP.ID P.ID date
1 123 xxab AAC 20121110
2 214 xxac JGK 20121110
3 543 xxad DIF 20121110
4 325 xxae ADL 20121110
5 123 xxaf AAC 20121110
6 214 xxaq JGS 20121110
The unique id is based on the combination of the DS.ID and the OP.ID, so that DS.ID can be repeated but the combination of DS.ID and OP.ID will not. I want to find the instances where P.ID changes. Also, the combination of DS.ID and OP.ID will not necessarily be in the same row.
So, first I'd rbind to create a dataframe, then I'd want to melt with dcast. I'd want to end up with columns of DS.ID and OP.ID as the unique ID, and then columns of both dates wit the values for each one.
df12 <- rbind.fill(df1,df2)
Solution
If all you want is to compare when there is a difference in P.ID, you can just merge by the two common columns, and then compare:
# Convert from factor to character.
df1$P.ID<-as.character(df1$P.ID)
df2$P.ID<-as.character(df2$P.ID)
# Merge
compare.df<-merge(df1,df2,by=c('DS.ID','OP.ID'))
# Find differences.
compare.df[compare.df$P.ID.x!=compare.df$P.ID.y,]
# DS.ID OP.ID P.ID.x date.x P.ID.y date.y
# 4 214 xxaq JGR 20121111 JGS 20121110
