Add insert a column between two columns in a data frame

Question

I have a data frame that has columns a  b  and c  I d like to add a new column d between b and c   I know I could just add d at the end by using cbind but how can I insert it in between two columns

User · Answer

You can do it like below -  df  lt - data frame a 1 4  b 5 8  c 9 12  df  d    lt - seq 10 13  df  lt - df  c  a   b   d   c

User · Answer

I would suggest you to use the function add column   from the tibble package   library tibble  dataset  lt - data frame a   1 5  b   2 6  c 3 7  add column dataset  d   4 8   after   2    Note  that you can use column names instead of column index    add column dataset  d   4 8   after    b     Or use argument  before instead of  after if more convenient   add column dataset  d   4 8   before    c

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Create an example data frame and add a column to it   df   data frame a   seq 1  3   b   seq 4 6   c   seq 7 9   df  d    lt - seq 10 12  df    a b c  d 1 1 4 7 10 2 2 5 8 11 3 3 6 9 12   Rearrange by column index  df   colnames df  c 1 2 4 3      or by column name  df   c  a    b    d    c      The result is    a b  d c 1 1 4 10 7 2 2 5 11 8 3 3 6 12 9

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When you can not assume that column b comes before c you can use match to find the column number of both  min to get the lower column number and seq len to get a sequence until this column  Then you can use this index first as a positive subset  than place the new column d and then use the sequence again as a negative subset  i  lt - seq len min match c  quot b quot    quot c quot    colnames x     data frame x i   d  x -i    cbind x i   d  x -i    Alternative    a b  d c  1 1 4 10 7  2 2 5 11 8  3 3 6 12 9  In case you know that column b comes before c you can place the new column d after b  i  lt - seq len match  quot b quot   colnames x    data frame x i   d  x -i      a b  d c  1 1 4 10 7  2 2 5 11 8  3 3 6 12 9  Data  x  lt - data frame a   1 3  b   4 6  c   7 9  d  lt - 10 12

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You would like to add column z to the old data frame  old df  defined by columns x and y    z   rbinom 1000  5  0 25  old df  lt - data frame x   c 1 1000   y   rnorm 1 1000   head old df    Define a new data frame called new df  new df  lt - data frame x   old df  1   z  y   old df  2   head new df

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Here is a an example of how to move a column from last to first position  It combines   with ncol  I thought it would be useful to have a very short answer here for the busy reader   d   mtcars d   c ncol d   1  ncol d -1

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For what it s worth  I wrote a function to do this    removed     I have now updated this function with before and after functionality and defaulting place to 1  It also has data table compatability           FUNCTION  InsertDFCol colName  colData  data  place   1  before  after    DESCRIPTION  Takes in a data  a vector of data  a name for that vector and a place to insert this vector into   the data frame as a new column  If you put place   3  the new column will be in the 3rd position and push the current   3rd column up one  and each subsuquent column up one   All arguments must be set  Adding a before and after   argument that will allow the user to say where to add the new column  before or after a particular column    Please note that if before or after is input  it WILL override the place argument if place is given as well  Also  place   defaults to adding the new column to the front         InsertDFCol  lt - function colName  colData  data  place   1  before  after         A check on the place argument    if  length names data    lt  place  stop  The place argument exceeds the number of columns in the data for the InsertDFCol function  Please check your place number     if  place  lt   0  amp    missing before      missing after     stop  You cannot put a column into the 0th or less than 0th position  Check your place argument      if  place    1    0  amp    missing before      missing after     stop  Your place value was not an integer      if    missing before    amp   missing after   stop  You cannot designate a before AND an after argument in the same function call  Please use only one or the other         Data Table compatability    dClass  lt - class data    data  lt - as data frame data       Creating booleans to define whether before or after is given    useBefore  lt -  missing before    useAfter  lt -  missing after       If either of these are true  then we are using the before or after argument  run the following code    if  useBefore   useAfter           Checking the before after argument if given  Also adding regular expressions      if  useBefore    CheckChoice before  names data     before  lt - paste0      before             if  useAfter    CheckChoice after  names data     after  lt - paste0      after                If before or after is given  replace  place  with the appropriate number      if  useBefore    newPlace  lt - grep before  names data     if  length newPlace   gt  1    stop  Your before argument matched with more than one column name  Do you have duplicate column names            if  useAfter    newPlace  lt - grep after  names data     if  length newPlace   gt  1    stop  Your after argument matched with more than one column name  Do you have duplicate column names            if  useBefore  place  lt - newPlace   Overriding place      if  useAfter  place  lt - newPlace   1   Overriding place            Making the new column    data   colName   lt - colData      Finding out how to reorder this      The if statement handles the case where place   1    currentPlace  lt - length names data     Getting the place of our data  which should have been just added at the end     if  place    1         colOrder  lt - c currentPlace  1  currentPlace - 1        else if  place    currentPlace      If the place to add the new data was just at the end of the data  Which is stupid   but we ll add support anyway       colOrder  lt - 1 currentPlace      else     Every other case       firstHalf  lt - 1  place - 1    Finding the first half on columns that come before the insertion      secondHalf  lt - place  currentPlace - 1    Getting the second half  which comes after the insertion      colOrder  lt - c firstHalf  currentPlace  secondHalf    Putting that order together            Reordering the data    data  lt - subset data  select   colOrder       Data Table compatability    if  dClass 1      data table   data  lt - as data table data       Returning    return data         I realized I also did not include CheckChoice           FUNCTION  CheckChoice names  dataNames  firstWord     Oops  message   TRUE                                                                                                   DESCRIPTION  Takes the column names of a data frame and checks to make sure whatever  choice  you made  be it    your choice of dummies or your choice of chops  is actually in the data frame columns  Makes troubleshooting easier     This function is also important in prechecking names to make sure the formula ends up being right  Use it after    adding in new data to check the  choose  options  Set firstWord to the first word you want said before an exclamation point    The warn argument  previously message  can be set to TRUE if you only want to         CheckChoice  lt - function names  dataNames  firstWord    Oops   warn   FALSE       for  name in names         if  warn    TRUE    if   name  in  dataNames     warning paste0 firstWord     The column value argument     name     was not valid OR not in your data  Check your input  This is a warning message of that             if  warn    FALSE    if   name  in  dataNames     stop paste0 firstWord     The column value argument      name     was not valid OR not in your data  Check your input

User · Answer

You can use the append   function to insert items into vectors or lists  dataframes are lists   Simply   df  lt - data frame a c 1 2   b c 3 4   c c 5 6    df  lt - as data frame append df  list d df b df c   after 2     Or  if you want to specify the position by name use which   df  lt - as data frame append df  list d df b df c   after which names df    b

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Here s a quick and dirty way of inserting a column in a specific position on a data frame  In my case  I have 5 columns in the original data frame  c1  c2  c3  c4  c5 and I will insert a new column c2b between c2 and c3   1  Let s first create the test data frame    gt  dataset  lt - data frame c1   1 5  c2   2 6  c3 3 7  c4 4 8  c5 5 9   gt  dataset   c1 c2 c3 c4 c5 1  1  2  3  4  5 2  2  3  4  5  6 3  3  4  5  6  7 4  4  5  6  7  8 5  5  6  7  8  9   2  Add the new column c2b at the end of our data frame    gt  dataset c2b  lt - 10 14  gt  dataset   c1 c2 c3 c4 c5 c2b 1  1  2  3  4  5  10 2  2  3  4  5  6  11 3  3  4  5  6  7  12 4  4  5  6  7  8  13 5  5  6  7  8  9  14   3  Reorder the data frame based on column indexes  In my case  I want to insert the new column  6  between existing columns 2 and 3  I do that by addressing the columns on my data frame using the vector c 1 2  6  3 5  which is equivalent to c 1  2  6  3  4  5     gt  dataset  lt - dataset  c 1 2  6  3 5    gt  dataset   c1 c2 c2b c3 c4 c5 1  1  2  10  3  4  5 2  2  3  11  4  5  6 3  3  4  12  5  6  7 4  4  5  13  6  7  8 5  5  6  14  7  8  9   There

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data1  lt - data frame col1 1 4  col2 5 8  col3 9 12  row names data1   lt - c  row1   row2   row3   row4   data1 data2  lt - data frame col1 21 24  col2 25 28  col3 29 32  row names data2   lt - c  row1   row2   row3   row4   data2 insertPosition   2 leftBlock  lt - unlist data1  1  insertPosition-1    insertBlock  lt - unlist data2  1 length data2 1      rightBlock  lt - unlist data1  insertPosition length data1 1      newData  lt - matrix c leftBlock  insertBlock  rightBlock   nrow length data1  1    byrow FALSE  newData

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Easy solution  In a data frame with 5 columns  If you want insert another column between 3 and 4       tmp  lt - data   1 3  tmp example  lt - NA   or any value  data  lt - cbind tmp  data   4 5

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This function inserts one zero column between all  pre-existent columns in a data frame   insertaCols lt -function dad        nueva lt -as data frame matrix rep 0 nrow daf  ncol daf  2   ncol ncol daf  2        for k in 1 ncol daf             nueva   k 2 -1  daf  k           colnames nueva   k 2 -1  colnames daf  k                 return nueva

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R has no functionality to specify where a new column is added  E g   mtcars mycol lt - foo   It always is added as last column  Using other means  e g   dplyr s select    you can move the mycol to a desired position  This is not ideal and R may want to try to change that in the future

User · Answer

Add in your new column   df d  lt - list data   Then you can reorder them   df  lt - df   c  a    b    d    c

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You can reorder the columns with    or present the columns in the order that you want   d  lt - data frame a 1 4  b 5 8  c 9 12  target  lt - which names d      b   1  cbind d  1 target drop F   data frame d 12 15   d   target 1  length d  drop F      a b  d  c 1 1 5 12  9 2 2 6 13 10 3 3 7 14 11 4 4 8 15 12

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Presuming that c always immediately follows b  this code will add a column after b no matter where b is in your data frame    gt  test  lt - data frame a 1 b 1 c 1   gt  test   a b c 1 1 1 1   gt  bspot  lt - which names test    b     gt  data frame test 1 bspot  d 2 test  bspot 1  ncol test      a b d c 1 1 1 2 1   Or possibly more naturally   data frame append test  list d 2   after match  b   names test

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df  lt - data frame a c 1 2   b c 3 4   c c 5 6   df   gt     mutate d  a 2    gt     select a  b  d  c    results    a b   d c 1 1 3 0 5 5 2 2 4 1 0 6   I suggest to use dplyr  select after dplyr  mutate  It has many helpers to select de-select subset of columns   In the context of this question the order by which you select will be reflected in the output data frame

[r] Add (insert) a column between two columns in a data.frame

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