replace value in dataframe based on another data frame

Question

I have the following two dataframes:

>df1<-data.frame(A=c(0,0,0),B=c(0,201,0),C=c(0,467,0))
  A   B   C
1 0   0   1
2 0 201 467
3 0   0   0

>df2<-data.frame(A=c(201,467),B=c('abc','def'))
    A   B
1 201 abc
2 467 def

I would like to replace the values in df1 using matching "B" values in df2, creating a dataframe that looks like this:

   A   B   C
1 NA  NA  NA
2 NA abc def
3 NA  NA  NA

I can accomplish this on a column by column basis using the following code:

>df2$B[match(df1$B,df2$A)]

Unfortunately, I am working with a massive dataset and would therefore prefer to match all of the columns at once. Any help would be much appreciated.

flodel · Accepted Answer · 2013-05-06 22:42:03Z

3

You can do:

df1[] <- setNames(df2$B, df2$A)[as.character(unlist(df1))]

answered May 6, 2013 at 22:42

flodel

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Tyler Rinker · Accepted Answer · 2013-05-06 22:59:35Z

2

Another possible solution:

df1<-data.frame(A=c(0,0,0),B=c(0,201,0),C=c(0,467,0))
df2<-data.frame(A=c(201,467),B=c('abc','def'))

library(qdap)
apply(df1, 2, lookup, df2)

## > apply(df1, 2, lookup, df2)
##      A  B     C    
## [1,] NA NA    NA   
## [2,] NA "abc" "def"
## [3,] NA NA    NA

answered May 6, 2013 at 22:59

Tyler Rinker

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