[R] create unique ID for each group

[arun]

Hi,

Try this:
dat1<- read.table(text="
ObsNumber     ID          Weight
     1                 0001         12
     2                 0001          13
     3                 0001           14
     4                  0002         16
      5                 0002         17
",sep="",header=TRUE,colClass=c("numeric","character","numeric"))
dat2<- read.table(text="
ID               Height
0001            3.2
0001             2.6
0001             3.2
0002             2.2
0002              2.6
",sep="",header=TRUE,colClass=c("character","numeric")) 
dat1$UniqueID<-with(dat1,as.character(interaction(ID,ObsNumber,sep="_")))
 dat2$UniqueID<-with(dat2,as.character(interaction(ID,rownames(dat2),sep="_")))
 dat2
#    ID Height UniqueID
#1 0001    3.2   0001_1
#2 0001    2.6   0001_2
#3 0001    3.2   0001_3
#4 0002    2.2   0002_4
#5 0002    2.6   0002_5
A.K.



----- Original Message -----
From: Ye Lin <yelin at lbl.gov>
To: R help <r-help at r-project.org>
Cc: 
Sent: Tuesday, May 7, 2013 1:54 PM
Subject: [R] create unique ID for each group

Hey All,

I have a dataset(dat1) like this:

ObsNumber     ID          Weight
     1                 0001         12
     2                 0001          13
     3                 0001           14
     4                  0002         16
      5                 0002         17

And another dataset(dat2) like this:

ID               Height
0001            3.2
0001             2.6
0001             3.2
0002             2.2
0002              2.6

I want to merge dat1 and dat2 based on "ID" in order, I know "match" only
returns the first match it finds. So I am thinking create unique ID col in
dat2 and dat2, then merge. But I dont know how to do that so it can be like
this:

dat1:

ObsNumber     ID          Weight  UniqueID
     1                 0001         12         0001_1
     2                 0001          13        0001_2
     3                 0001           14       0001_3
     4                  0002         16         0002_1
      5                 0002         17         0002_1

dat2:

ID               Height   UniqueID
0001            3.2          0001_1
0001             2.6         0001_2
0001             3.2         0001_3
0002             2.2         0002_1
0002              2.6        0002_2

Or if it is possible to merge dat1 and dat2 by matching "ID" but return the
match in order that would be great!

Thanks for your help!

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