R help - Jan 2012 - add column with values found in another data frame

I am positive this problem has a very simple solution, but I have been
unable to find it, so I am asking for your help. I need to know how to look
something up in one data frame and add it as a column in another.  If I have
a data frame that looks like this:
> frame1
  ID  score  test age
1  Guy1 10 1  20
2 Guy1 13 2  20
3 Guy2 9 1  33
4 Guy2 11 2  33

and another frame that looks like this:
> frame2
  ID
1 Guy1
2 Guy2

How do I add a column to frame2 so it looks like this:

  ID age
1 Guy1 20
2 Guy2 33

I know this must be simple, but I couldn't find the solution by searching.

thanks so much
Jeremy


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Hi Jeremy,

Try
> frame1 <- structure(list(ID = structure(c(1L, 1L, 2L, 2L), .Label
c("Guy1",
"Guy2"), class = "factor"), score = c(10L, 13L, 9L, 11L),
test = c(1L,
2L, 1L, 2L), age = c(20L, 20L, 33L, 33L)), .Names = c("ID",
"score",
"test", "age"), class = "data.frame", row.names =
c("1", "2",
"3", "4"))
> frame2 <- structure(list(ID = structure(1:2, .Label =
c("Guy1", "Guy2"),
class = "factor")),
.Names = "ID", class = "data.frame", row.names =
c("1", "2"))
> merge(frame1, frame2, by = "ID"))
    ID score test age
1 Guy1    10    1  20
2 Guy1    13    2  20
3 Guy2     9    1  33
4 Guy2    11    2  33
> subset(frame1, ID %in% frame2$ID, select = c(ID, age))
    ID age
1 Guy1  20
2 Guy1  20
3 Guy2  33
4 Guy2  33

See ?subset and ?merge for more information.

HTH,
Jorge.-


On Sat, Jan 14, 2012 at 3:51 PM, jdog76 <> wrote:
>  I am positive this problem has a very simple solution, but I have been
> unable to find it, so I am asking for your help. I need to know how to look
> something up in one data frame and add it as a column in another.  If I
> have
> a data frame that looks like this:
>
> > frame1
>  ID  score  test age
> 1  Guy1 10 1  20
> 2 Guy1 13 2  20
> 3 Guy2 9 1  33
> 4 Guy2 11 2  33
>
> and another frame that looks like this:
>
> > frame2
>  ID
> 1 Guy1
> 2 Guy2
>
> How do I add a column to frame2 so it looks like this:
>
>  ID age
> 1 Guy1 20
> 2 Guy2 33
>
> I know this must be simple, but I couldn't find the solution by
searching.
>
> thanks so much
> Jeremy
>
>
> --
> View this message in context:
>
http://r.789695.n4.nabble.com/add-column-with-values-found-in-another-data-frame-tp4295626p4295626.html
> Sent from the R help mailing list archive at Nabble.com.
>
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

jdog76 wrote
> 
> I am positive this problem has a very simple solution, but I have been
> unable to find it, so I am asking for your help. I need to know how to
> look something up in one data frame and add it as a column in another.  If
> I have a data frame that looks like this:
> 
>> frame1
>   ID  score  test age
> 1  Guy1 10 1  20
> 2 Guy1 13 2  20
> 3 Guy2 9 1  33
> 4 Guy2 11 2  33
> 
> and another frame that looks like this:
> 
>> frame2
>   ID
> 1 Guy1
> 2 Guy2
> 
> How do I add a column to frame2 so it looks like this:
> 
>   ID age
> 1 Guy1 20
> 2 Guy2 33
> 
> I know this must be simple, but I couldn't find the solution by
searching.
> 
> thanks so much
> Jeremy
> 
How about ....

frame2$age = frame1[match(frame2$ID, frame1$ID),"age"]

print(frame2)
    ID age
1 Guy1  20
2 Guy2  33

HTH

Pete



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Thanks so much Jorge and Pete !


Pete Brecknock wrote
> 
> 
> frame2$age = frame1[match(frame2$ID, frame1$ID),"age"]
> 
> 
This match function was exactly what I needed to know!


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