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$C <-c(1,1,1,2,2,3,3,3,3,3,4,4)
I only show 12 rows, my real data frame has over 1000 rows, I can not manually
to add column C.
It should be easy, but I can not figure out. Can you help me?
Thanks,
Ding
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Hi,
Here's one way to approach it, using the coercion of factor to numeric.
Note that I changed your data.frame() statement to avoid coercing
strings to factors, just to make it simpler to set the levels.
dat1 <-data.frame(N=seq(1, 12,1), B=c("29_log","29_log",
"29_log",
"27_cat", "27_cat", "1_log", "1_log",
"1_log", "1_log", "1_log",
"3_cat", "3_cat"), stringsAsFactors=FALSE)
dat1$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 <ycding at 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$C <-c(1,1,1,2,2,3,3,3,3,3,4,4)
>
> I only show 12 rows, my real data frame has over 1000 rows, I can not
manually to add column C.
>
> It should be easy, but I can not figure out. Can you help me?
>
> Thanks,
>
> Ding
>
--
Sarah Goslee
http://www.functionaldiversity.org
Hi Sarah,
Thank you so much!! I got your good ideas.
Ding
-----Original Message-----
From: Sarah Goslee [mailto:sarah.goslee at gmail.com]
Sent: Friday, May 11, 2018 11:40 AM
To: Ding, Yuan Chun
Cc: r-help mailing list
Subject: Re: [R] add one variable to a data frame
[Attention: This email came from an external source. Do not open attachments or
click on links from unknown senders or unexpected emails.]
Hi,
Here's one way to approach it, using the coercion of factor to numeric.
Note that I changed your data.frame() statement to avoid coercing strings to
factors, just to make it simpler to set the levels.
dat1 <-data.frame(N=seq(1, 12,1), B=c("29_log","29_log",
"29_log", "27_cat", "27_cat", "1_log",
"1_log", "1_log", "1_log", "1_log",
"3_cat", "3_cat"), stringsAsFactors=FALSE)
dat1$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 <ycding at 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$C <-c(1,1,1,2,2,3,3,3,3,3,4,4)
>
> I only show 12 rows, my real data frame has over 1000 rows, I can not
manually to add column C.
>
> It should be easy, but I can not figure out. Can you help me?
>
> Thanks,
>
> Ding
>
--
Sarah Goslee
http://www.functionaldiversity.org
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Sarah et. al.: As a matter of aesthetics (i.e. my personal ocd-ness) I prefer using the public API of an object, i.e. *not* to makes use of the representation of a factor as essentially an integer vector with labels, but rather to use its documented behavior. (Feel free to ignore this remark!) Anyway,>cumsum(!duplicated(dat1$B))[1] 1 1 1 2 2 3 3 3 3 3 4 4 will do it. This is very efficient (almost certainly of no concern here, btw). But the price for this efficiency is that it depends completely on the data beig grouped in order as the OP showed. It will fail if this is not the case. If, for example, the data appeared as:> set.seed(1234) > ix <- sample(1:12)> dat1[ix,]N B 2 2 29_log 7 7 1_log 11 11 3_cat 6 6 1_log 10 10 1_log 5 5 27_cat 1 1 29_log 12 12 3_cat 3 3 29_log 8 8 1_log 4 4 27_cat 9 9 1_log then Don's solution will still work. The above doesn't. So this emphasizes the importance of precisely and completely specifying the nature of your data. Hence: which is it? -- all the groups appearing together or possibly mixed up? But I have another question: why do this at all? The new column adds no new information -- I believe that anything you want to do with the integer codes can be done in R with the original factor representation (and just as efficiently, as Sarah's "aesthetically displeasing to Bert" suggestion makes clear). Note: counterexample welcome! So as AFAICS, there is no need for this at all. Cheers, Bert Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) On Fri, May 11, 2018 at 11:39 AM, Sarah Goslee <sarah.goslee at gmail.com> wrote:> 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))$lengths) > > (That second will work even if B is a factor.) > > > dat1 > N B C1 C2 > 1 1 29_log 1 1 > 2 2 29_log 1 1 > 3 3 29_log 1 1 > 4 4 27_cat 2 2 > 5 5 27_cat 2 2 > 6 6 1_log 3 3 > 7 7 1_log 3 3 > 8 8 1_log 3 3 > 9 9 1_log 3 3 > 10 10 1_log 3 3 > 11 11 3_cat 4 4 > 12 12 3_cat 4 4 > > > Sarah > > On Fri, May 11, 2018 at 1:52 PM, Ding, Yuan Chun <ycding at coh.org> wrote: > > Hi All, > > > > I have a data frame dat1: > > dat1 <-data.frame(N=seq(1, 12,1), B=c("29_log","29_log", "29_log", > "27_cat", "27_cat", > > > "1_log", "1_log", "1_log", "1_log", "1_log", > > > "3_cat", "3_cat")) > > > > Then I need to add one column or variable to reflect uniqueness of B > variable in sequential order as below. > > dat1$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 > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > 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]]