combining two data frames of different lengths

Question

I have two data frames  The first is of only one column and 10 rows  The second is of 3 columns and 50 rows   When I try to combine this by using cbind  it gives this error      Error in data frame      check names   FALSE      Can anyone suggest another function to do this  P S I have tried this using lists too  but it gives the same error   The data frame consisting of 3 columns should be the first 3 columns in a CSV file  whereas the data frame with one column should be the fourth column in that file  when I write with the write table function  The first 3 columns have 50 rows and the fourth column should occupy the first 10 rows

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My idea is to get max of rows count of all data frames and next append empty matrix to every data frame if need  This method doesn t require additional packages  only base is used  Code looks following   list df  lt - list data frame a   1 10   data frame a   1 5   data frame a   1 3    max rows  lt - max unlist lapply list df  nrow   use names   F    list df  lt - lapply list df  function x        na count  lt - max rows - nrow x      if  na count  gt  0L            na dm  lt - matrix NA  na count  ncol x           colnames na dm   lt - colnames x          rbind x  na dm        else           x           do call cbind  list df         a  a  a   1   1  1  1   2   2  2  2   3   3  3  3   4   4  4 NA   5   5  5 NA   6   6 NA NA   7   7 NA NA   8   8 NA NA   9   9 NA NA   10 10 NA NA

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i had similar problem  i matched the entries in a particular column of two data sets and cbind only if it matched   For two data sets  data1  amp  data2  i am adding a column in data1 from data2 after comparing first column of both   for i in 1 nrow data1     for  j in 1 nrow data2       if  data1 i 1   data2 j 1   data1 i 3  lt - data2 j 2

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It s not clear to me at all what the OP is actually after  given the follow-up comments  It s possible they are actually looking for a way to write the data to file   But let s assume that we re really after a way to cbind multiple data frames of differing lengths   cbind will eventually call data frame  whose help files says      Objects passed to data frame should have the same number of rows  but   atomic vectors  factors and character vectors protected by I will be   recycled a whole number of times if necessary  including as from R   2 9 0  elements of list arguments     so in the OP s actual example  there shouldn t be an error  as R ought to recycle the shorter vectors to be of length 50  Indeed  when I run the following   set seed 1  a  lt - runif 50  b  lt - 1 50 c  lt - rep LETTERS 1 5  length out   50  dat1  lt - data frame a b c  dat2  lt - data frame d   runif 10  e   runif 10   cbind dat1 dat2    I get no errors and the shorter data frame is recycled as expected  However  when I run this   set seed 1  a  lt - runif 50  b  lt - 1 50 c  lt - rep LETTERS 1 5  length out   50  dat1  lt - data frame a b c  dat2  lt - data frame d   runif 9   e   runif 9   cbind dat1 dat2    I get the following error   Error in data frame      check names   FALSE       arguments imply differing number of rows  50  9   But the wonderful thing about R is that you can make it do almost anything you want  even if you shouldn t  For example  here s a simple function that will cbind data frames of uneven length and automatically pad the shorter ones with NAs   cbindPad  lt - function       args  lt - list      n  lt - sapply args nrow  mx  lt - max n  pad  lt - function x  mx       if  nrow x   lt  mx           nms  lt - colnames x          padTemp  lt - matrix NA  mx - nrow x   ncol x           colnames padTemp   lt - nms         if  ncol x   0              return padTemp            else           return rbind x padTemp                         else          return x          rs  lt - lapply args pad mx  return do call cbind rs       which can be used like this   set seed 1  a  lt - runif 50  b  lt - 1 50 c  lt - rep LETTERS 1 5  length out   50  dat1  lt - data frame a b c  dat2  lt - data frame d   runif 10  e   runif 10   dat3  lt - data frame d   runif 9   e   runif 9   cbindPad dat1 dat2 dat3    I make no guarantees that this function works in all cases  it is meant as an example only   EDIT  If the primary goal is to create a csv or text file  all you need to do it alter the function to pad using    rather than NA and then do something like this   dat  lt - cbindPad dat1 dat2 dat3  rs  lt - as data frame apply dat 1 function x  paste as character x  collapse           and then use write table on rs

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Refering to Andrie s answer  suggesting to use plyr  rbind fill    Combined with t   you have something like cbind fill    which is not part of plyr  that will construct your data frame with consideration of identical case numbers

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In the plyr package there is a function rbind fill that will merge data frames and introduce NA for empty cells   library plyr  combined  lt - rbind fill mtcars c  mpg    wt     mtcars c  wt    cyl     combined 25 40         mpg    wt cyl 25 19 2 3 845  NA 26 27 3 1 935  NA 27 26 0 2 140  NA 28 30 4 1 513  NA 29 15 8 3 170  NA 30 19 7 2 770  NA 31 15 0 3 570  NA 32 21 4 2 780  NA 33   NA 2 620   6 34   NA 2 875   6 35   NA 2 320   4

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I don t actually get an error with this   a  lt - as data frame matrix c sample letters 50  replace T  runif 100    nrow 50   b  lt - sample letters 10  replace T  c  lt - cbind a b    I used letters incase joining all numerics had different functionality  which it didn t   Your   first data frame   which is actually just a vector   is just repeated 5 times in that 4th column     But all the comments from the gurus to the question are still relevant

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Just my 2 cents  This code combines two matrices or data frames into one  If one data structure have lower number of rows then missing rows will be added with NA values   combine df  lt - function x  y        rows x  lt - nrow x      rows y  lt - nrow y      if  rows x  gt  rows y            diff  lt - rows x - rows y         df na  lt - matrix NA  diff  ncol y           colnames df na   lt - colnames y          cbind x  rbind y  df na         else           diff  lt - rows y - rows x         df na  lt - matrix NA  diff  ncol x           colnames df na   lt - colnames x          cbind rbind x  df na   y           df1  lt - data frame 1 10  row names   1 10  df2  lt - data frame 1 5  row names   10 14  combine df df1  df2

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Hope this will work for you   You can use library qpcR  for combining two matrix with unequal size   resultant matrix  lt - qpcR   cbind na matrix1  matrix2    NOTE - The resultant matrix will be of size of matrix2

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I think I have come up with a quite shorter solution   Hope it helps someone   cbind na lt -function df1  df2       Collect all unique rownames   total rownames lt -union x   rownames x   df1  y   rownames x df2       Create a new dataframe with rownames   df lt -data frame row names   total rownames      Get absent rownames for both of the dataframe   absent names 1 lt -setdiff x   rownames df1  y   rownames df     absent names 2 lt -setdiff x   rownames df2  y   rownames df       Fill absents with NAs   df1 fixed lt -data frame row names   absent names 1 matrix data   NA nrow   length absent names 1  ncol ncol df1      colnames df1 fixed  lt -colnames df1    df1 lt -rbind df1 df1 fixed     df2 fixed lt -data frame row names   absent names 2 matrix data   NA nrow   length absent names 2  ncol ncol df2      colnames df2 fixed  lt -colnames df2    df2 lt -rbind df2 df2 fixed      Finally cbind into new dataframe   df lt -cbind df df1 rownames df    df2 rownames df       return df

[r] combining two data frames of different lengths

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