Adding a column to a dataframe in R

Question

I have the following dataframe  df    start     end 1    14379   32094 2   151884  174367 3   438422  449382 4   618123  621256 5   698271  714321 6   973394  975857 7   980508  982372 8   994539  994661 9  1055151 1058824                                             And a long vector with numeric values  vec    I would like to add to each row another column  with the mean of the values in the corresponding places in vec  for example  the first row will have mean vec 14379 32094    I have tried playing with transform but wasn t able to accomplish this simple task

User · Answer

Even if that s a 7 years old question  people new to R should consider using the data table  package   A data table is a data frame so all you can do for to a data frame you can also do  But many think are ORDERS of magnitude faster with data table   vec  lt - 1 10 library data table  DT  lt - data table start c 1 3 5 7   end c 2 6 7 9   DT  new  apply DT 1 function row  mean vec  row 1    row 2

User · Answer

That is a pretty standard use case for apply     R gt  vec  lt - 1 10 R gt  DF  lt - data frame start c 1 3 5 7   end c 2 6 7 9   R gt  DF newcol  lt - apply DF 1 function row  mean vec  row 1    row 2       R gt  DF   start end newcol 1     1   2    1 5 2     3   6    4 5 3     5   7    6 0 4     7   9    8 0 R gt     You can also use plyr if you prefer but here is no real need to go beyond functions from base R

[r] Adding a column to a dataframe in R

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