Create an ID (row number) column

Question

I need to create a column with unique ID, basically add the row number as an own column. My current data frame looks like this:

   V1  V2
1  23  45
2  45  45
3  56  67

How to make it look like this:

V1  V2  V3
1  23  45
2  45  45
3  56  67

?

Many thanks

Answer 1

Two tidyverse alternatives (using sgibb's example data):

tibble::rowid_to_column(d, "ID")

which gives:

  ID V1 V2
1  1 23 45
2  2 45 45
3  3 56 67

Or:

dplyr::mutate(d, ID = row_number())

which gives:

  V1 V2 ID
1 23 45  1
2 45 45  2
3 56 67  3

As you can see, the rowid_to_column-function adds the new column in front of the other ones while the mutate&row_number()-combo adds the new column after the others.

---

And another base R alternative:

d$ID <- seq_along(d[,1])

Answer 2

You could also do this using dplyr:

DF <- mutate(DF, id = rownames(DF))

Answer 3

Many presented their ideas, but I think this is the sortest and simplest code for this task:

data$ID <- 1:nrow(data)

One line. The one and only.

Answer 4

data.table solution

Easier syntax and much faster

library(data.table)

dt <- data.table(V1=c(23, 45, 56), V2=c(45, 45, 67))

setnames(dt, c("V2", "V3")) # changing column names
dt[, V1 := .I] # Adding ID column

Answer 5

Hope this will help. Shortest and best way to create ID column is:

dataframe$ID <- seq.int(nrow(dataframe))

Answer 6

Here is a solution that keeps the dplyr piping format and places id in the first column, which may be preferred.

d %>% 
  mutate(id = rownames(.)) %>% 
  select(id, everything())

Answer 7

If you're starting without named rows in your df, the tidy way is:

df %>% 
  mutate(id = row_number()) %>% 
  select(id, everything())

Answer 8

The function rownames_to_column() moves rownames into a column; found in the tidyverse package (docs).

rownames_to_column(DF, "my_column_name")

Use column_to_rownames() for the reverse operation.

Answer 9

If your database is not too large this will work

# Load sample data
Dt1 <- tibble(V1=c(23,45,56),V2=c(45,45,67))
# Create Separate Tibble with row numbers
Dt2 <- tibble(id=seq(1:nrow(Dt1)))
# Join together
Dt3 <- cbind(Dt2,Dt1)