Adding identifer (metadata) columns to a long format data set

问题

Given a long format data set like this:

ID_2<-c('A','A','A','B','B','C','E','E','F','F','H','H','H')
Type<-c('Blk','Wht','Gre','Blk','Wht','Blk','Blk','Wht','Blk','Wht','Wht','Blk','Gre')
Count<-c(1,2,2,1,2,1,2,1,2,1,2,1,2)
DF2<-data.frame(ID_2,Type,Count)

I would like to add a specific set of metadata for each unique ID (ID_2). The metadata would be found in a separate data frame like so:

Year<-c(2005,2005,2006,2006,2007,2008,2008,2008)
Location<-c('EAST','EAST','WEST','WEST','NORTH','EAST','EAST','EAST')
Site<-c(1,2,3,4,5,6,7,8)
ID_1<-c('A','B','C','NAN','E','F','NAN','H')
DF1<-data.frame(Year,Location,Site,ID_1)

I would like to add the metadata from DF1 to the long format of DF2 (matching up ID_1 and ID_2), so that each row of DF2 contains the proper metadata from DF1

I also need to deal with the blank locations, so that any unique site number from DF_1 that does not have a corresponding data entry in DF_2 gets a flagged entry. The end result would look like this:

Year  Location  Site  ID Type Count
2005     EAST    1    A  Blk     1
2005     EAST    1    A  Wht     2
2005     EAST    1    A  Gre     2
2005     EAST    2    B  Blk     1
2006     WEST    3    C  Blk     1
2007    NORTH    5    E  Blk     2
2007    NORTH    5    E  Wht     1
2008     EAST    6    F  Blk     2
2008     EAST    6    F  Wht     1
2008     EAST    8    H  Wht     2
2008     EAST    8    H  Blk     1
2008     EAST    8    H  Gre     2
2006     WEST    4  Flag Flag   -999
2008     EAST    7  Flag Flag   -999

回答1:

This appears to be a simple merge()

> merge(DF1, DF2, by.x = "ID_1", by.y = "ID_2", all = TRUE)
   ID_1 Year Location Site Type Count
1     A 2005     EAST    1  Blk     1
2     A 2005     EAST    1  Wht     2
3     A 2005     EAST    1  Gre     2
4     B 2005     EAST    2  Blk     1
5     B 2005     EAST    2  Wht     2
6     C 2006     WEST    3  Blk     1
7     E 2007    NORTH    5  Blk     2
8     E 2007    NORTH    5  Wht     1
9     F 2008     EAST    6  Blk     2
10    F 2008     EAST    6  Wht     1
11    H 2008     EAST    8  Wht     2
12    H 2008     EAST    8  Blk     1
13    H 2008     EAST    8  Gre     2
14  NAN 2006     WEST    4 <NA>    NA
15  NAN 2008     EAST    7 <NA>    NA

You'll have to do a little bit of extra work to replace the NA values with whatever you actually want to use.

来源：https://stackoverflow.com/questions/18001095/adding-identifer-metadata-columns-to-a-long-format-data-set

标签

dataframe

metadata