[R] add one variable to a data frame

Fri May 11 22:59:14 CEST 2018

Hi Don and Sarah,

Thanks a lot, I learned quite a few functions today.

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 = F)
dat1$C <-c(1,1,1,2,2,3,3,3,3,3,4,4)
#The match() function returns a vector of the position of first occurrence of the
#vector1 in vector2. If the element of the vector1 does not exist in vector2, 
#NA is returned.
dat1$don <- match(dat1$B, unique(dat1$B))

dat1$sarah1 <- as.numeric(factor(dat1$B, levels=unique(dat1$B)))

# rle, Compute the lengths and values of runs of equal values in a vector
# return a list with two elements, length of each value, and unique values
dat1$sarah2 <- rep(seq_len(length(unique(dat1$B))),
                   times=rle(as.vector(dat1$B))$lengths)

#seq_along(x) is the same as seq_len(length(x))
dat1$D <- rep(seq_along(unique(dat1$B)),
                   times=rle(as.vector(dat1$B))$lengths)

-----Original Message-----
From: MacQueen, Don [mailto:macqueen1 using llnl.gov] 
Sent: Friday, May 11, 2018 12:30 PM
To: Ding, Yuan Chun; Sarah Goslee
Cc: r-help mailing list
Subject: Re: [R] add one variable to a data frame

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-bounces using r-project.org on behalf of ycding using coh.org> wrote:

    Hi Sarah,

    Thank you so much!! I got your good ideas.

    Ding

    -----Original Message-----
    From: Sarah Goslee [mailto:sarah.goslee using 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 using 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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