Copy column but drop observations one row in R

Asked May 24 '19 at 00:44

Active May 24 '19 at 01:12

Viewed 25 times

Suppose I have a dataset like this

df <- data.frame(letters = LETTERS[1:5],
                 numbers = 6:10)
df
  letters numbers
1       A       6
2       B       7
3       C       8
4       D       9
5       E      10

I would like to copy a column, but droping observations one row. I could do this manually:

df$numbers2 <- c(0, df$numbers[-length(df$numbers))

To get this result:

df
  letters numbers numbers2
1       A       6        0
2       B       7        6
3       C       8        7
4       D       9        8
5       E      10        9

Is there a function to perform this task?

edited May 24 '19 at 01:12

neilfws

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asked May 24 '19 at 00:44

Bruno Pinheiro

2

`df$numbers2 <- dplyr::lag(df$numbers)` – M-- May 24 '19 at 00:47
`lag()` is exactly the function I was loonking for! Actually i used it before, but I was not remembering its name. Thank you very much! – Bruno Pinheiro May 24 '19 at 00:51
1

Or without packages, use `head` - `c(0,head(df$numbers,-1))` – thelatemail May 24 '19 at 00:51
1

Well if we agree on `library(dplyr)` then `df <- df %>% mutate(numbers2 = lag(numbers))` – M-- May 24 '19 at 00:51
The dplyr solution is ok for me. Without packages I did using `c(0, df$numbers[-length(df$numbers))`, because data could have n observations. – Bruno Pinheiro May 24 '19 at 00:54
@BrunoPinheiro - `head` deals with that, it just removes the last value. – thelatemail May 24 '19 at 00:55
@thelatemail Of corse!! `head(x, -1)`! I was not considering the "-1" argument. Very simple too! – Bruno Pinheiro May 24 '19 at 00:58

Copy column but drop observations one row in R

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