Sarah's solutions are good, and here's another, even more basic:
tmp1 <- unique(dat1$B)
tmp2 <- seq_along(tmp1)
dat1$C <- tmp2[ match( dat1$B, tmp1) ]
> dat1
N B C
1 1 29_log 1
2 2 29_log 1
3 3 29_log 1
4 4 27_cat 2
5 5 27_cat 2
6 6 1_log 3
7 7 1_log 3
8 8 1_log 3
9 9 1_log 3
10 10 1_log 3
11 11 3_cat 4
12 12 3_cat 4
As a single line command:
dat1$C <- seq(length(unique(dat1$B)))[ match( dat1$B, unique(dat1$B) )]
-Don
--
Don MacQueen
Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062
Lab cell 925-724-7509
On 5/11/18, 12:04 PM, "R-help on behalf of Ding, Yuan Chun"
<r-help-boun...@r-project.org on behalf of ycd...@coh.org> wrote:
Hi Sarah,
Thank you so much!! I got your good ideas.
Ding
-----Original Message-----
From: Sarah Goslee [mailto:sarah.gos...@gmail.com]
Sent: Friday, May 11, 2018 11:40 AM
To: Ding, Yuan Chun
Cc: r-help mailing list
Subject: Re: [R] add one variable to a data frame
[Attention: This email came from an external source. Do not open
attachments or click on links from unknown senders or unexpected emails.]
Hi,
Here's one way to approach it, using the coercion of factor to numeric.
Note that I changed your data.frame() statement to avoid coercing strings
to factors, just to make it simpler to set the levels.
dat1 <-data.frame(N=seq(1, 12,1), B=c("29_log","29_log", "29_log",
"27_cat", "27_cat", "1_log", "1_log", "1_log", "1_log", "1_log", "3_cat",
"3_cat"), stringsAsFactors=FALSE)
dat1$C1 <- as.numeric(factor(dat1$B, levels=unique(dat1$B)))
And here's a way using rle()
dat1$C2 <- rep(seq_len(length(unique(dat1$B))),
times=rle(as.vector(dat1$B))$lengths)
(That second will work even if B is a factor.)
> dat1
N B C1 C2
1 1 29_log 1 1
2 2 29_log 1 1
3 3 29_log 1 1
4 4 27_cat 2 2
5 5 27_cat 2 2
6 6 1_log 3 3
7 7 1_log 3 3
8 8 1_log 3 3
9 9 1_log 3 3
10 10 1_log 3 3
11 11 3_cat 4 4
12 12 3_cat 4 4
Sarah
On Fri, May 11, 2018 at 1:52 PM, Ding, Yuan Chun <ycd...@coh.org> wrote:
> Hi All,
>
> I have a data frame dat1:
> dat1 <-data.frame(N=seq(1, 12,1), B=c("29_log","29_log", "29_log",
"27_cat", "27_cat",
>
"1_log", "1_log", "1_log", "1_log", "1_log",
>
> "3_cat", "3_cat"))
>
> Then I need to add one column or variable to reflect uniqueness of B
variable in sequential order as below.
> dat1$C <-c(1,1,1,2,2,3,3,3,3,3,4,4)
>
> I only show 12 rows, my real data frame has over 1000 rows, I can not
manually to add column C.
>
> It should be easy, but I can not figure out. Can you help me?
>
> Thanks,
>
> Ding
>
--
Sarah Goslee
http://www.functionaldiversity.org
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