How can I convert row names into the first column?

Question

I have a data frame like this:

df
              VALUE              ABS_CALL DETECTION P-VALUE    
    1007_s_at "957.729231881542" "P"      "0.00486279317241156"
    1053_at   "320.632701283368" "P"      "0.0313356324173416" 
    117_at    "429.842323161046" "P"      "0.0170004527476119" 
    121_at    "2395.7364289242"  "P"      "0.0114473584876183" 
    1255_g_at "116.493632746934" "A"      "0.39799368200131"   
    1294_at   "739.927122116896" "A"      "0.0668649772942343"

I want to convert the row names into the first column. Currently I use something like this to make row names as the first column:

  d <- df
  names <- rownames(d)
  rownames(d) <- NULL
  data <- cbind(names,d)

Is there a single line to do this?

possible duplicate of R: converting row names in multiple data frames to column in data frame — rmuc8
– rmuc8, Commented Apr 8, 2015 at 9:50
You don't need extra packages, here's a one-liner: d <- cbind(rownames(d), data.frame(d, row.names=NULL)) — ssp3nc3r
– ssp3nc3r, Commented Oct 6, 2017 at 20:13

Dalija Prasnikar · Accepted Answer · 2024-05-24 19:56:35Z

259

Or you can use tibble's rownames_to_column which does the same thing as David's answer:

library(tibble)
df <- tibble::rownames_to_column(df, "VALUE")

Note: The earlier function called add_rownames() has been deprecated and is being replaced by tibble::rownames_to_column()

edited May 24, 2024 at 19:56

Dalija Prasnikar♦

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answered Apr 8, 2015 at 10:04

hrbrmstr

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2 Comments

David Arenburg Over a year ago

Not exactly the same, because it's not doing it by reference :)

Euler_Salter Over a year ago

This is great if one wants to stay within the tidyverse

David Arenburg · Accepted Answer · 2019-02-05 12:01:14Z

168

You can both remove row names and convert them to a column by reference (without reallocating memory using ->) using setDT and its keep.rownames = TRUE argument from the data.table package

library(data.table)
setDT(df, keep.rownames = TRUE)[]
#    rn     VALUE  ABS_CALL DETECTION     P.VALUE
# 1:  1 1007_s_at  957.7292         P 0.004862793
# 2:  2   1053_at  320.6327         P 0.031335632
# 3:  3    117_at  429.8423         P 0.017000453
# 4:  4    121_at 2395.7364         P 0.011447358
# 5:  5 1255_g_at  116.4936         A 0.397993682
# 6:  6   1294_at  739.9271         A 0.066864977

As mentioned by @snoram, you can give the new column any name you want, e.g. setDT(df, keep.rownames = "newname") would add "newname" as the rows column.

edited Feb 5, 2019 at 12:01

answered Apr 8, 2015 at 9:53

David Arenburg

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8 Comments

Swetabh Over a year ago

Use colnames(df)[1] <- "newname" to rename the first column if needed.

David Arenburg Over a year ago

@Swetabh Well, no. setnames(df, 1, "newname") is the data.table way.

s_baldur Over a year ago

@DavidArenburg Well, (at least) now you can do it in the same call setDT(df, keep.rownames = "newname")[]

s_baldur Over a year ago

@DavidArenburg found in documentation for as.data.table(): If TRUE, adds the input object's names as a separate column named "rn". keep.rownames = "id" names the column "id" instead

David Arenburg Over a year ago

@snoram good find, I'll make a PR regarding that to make docs consistent.

|

Jaap · Accepted Answer · 2017-10-06 19:42:59Z

124

A one line option is :

df$names <- rownames(df)

edited Oct 6, 2017 at 19:42

Jaap

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answered Mar 18, 2016 at 12:21

Emily

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4 Comments

Agaz Wani Over a year ago

I hope you are aware of the fact that it adds rownames as a column at the last, indeed not as a first column.

vasili111 Over a year ago

After to remove index use rownames(df) <- NULL

Aravindan Kalai Over a year ago

@vasili111 - could you explain what does it mean by 'to remove index' as I see no difference to the data table before (df$names <- rownames(df)) and after (rownames(df) <- NULL). Do you mean it stores the index column internally?

vasili111 Over a year ago

@AravindanKalai Hi. rownames(df) <- NULL will remove original row names. I was referring to row names.

drasc · Accepted Answer · 2017-03-30 17:55:32Z

43

Alternatively, you can create a new dataframe (or overwrite the current one, as the example below) so you do not need to use of any external package. However this way may not be efficient with huge dataframes.

df <- data.frame(names = row.names(df), df)

answered Mar 30, 2017 at 17:55

drasc

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1 Comment

Mark Miller Over a year ago

Or: df <- cbind(names = rownames(df), df)

ssp3nc3r · Accepted Answer · 2019-03-27 13:43:58Z

38

Moved my comment into an answer per suggestion above:

You don't need extra packages, here's a one-liner:

d <- cbind(rownames(d), data.frame(d, row.names=NULL))

answered Mar 27, 2019 at 13:43

ssp3nc3r

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Comments

Dima Lituiev · Accepted Answer · 2021-08-22 07:18:50Z

9

dplyr::as_tibble(df, rownames = "your_row_name") will give you even simpler result.

edited Aug 22, 2021 at 7:18

Dima Lituiev

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answered Jun 1, 2019 at 15:37

SteveS

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2 Comments

tjebo Over a year ago

@HectorHaffenden have edited this for the poster, because it's actually a nice suggestion.

Samuel Saari Over a year ago

"as_data_frame() was deprecated in tibble 2.0.0. Please use as_tibble() instead." Otherwise this is my favourite.

marianthi · Accepted Answer · 2022-01-23 19:38:42Z

7

Change data rownames as a real column

data <- data %>%
  rownames_to_column(var="the name you want")

answered Jan 23, 2022 at 19:38

marianthi

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Comments

M.Viking · Accepted Answer · 2022-09-08 01:34:21Z

5

df = data.frame(columnNameILike = row.names(df), df, row.names=NULL)

edited Sep 8, 2022 at 1:34

M.Viking

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answered Mar 12, 2021 at 20:09

Yale Liu

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1 Comment

Jun-Hoe Lee Sep 16 at 8:45

Thanks, this was the easiest and doesn't require any additional packages!

UseR10085 · Accepted Answer · 2020-07-02 05:37:17Z

3

Or by using DBIs sqlRownamesToColumn

library(DBI)
sqlRownamesToColumn(df)

edited Jul 2, 2020 at 5:37

UseR10085

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answered Nov 22, 2019 at 22:53

Agaz Wani

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