Convert data frame column to a vector

Question

I have a dataframe such as   a1   c 1  2  3  4  5  a2   c 6  7  8  9  10  a3   c 11  12  13  14  15  aframe   data frame a1  a2  a3    I tried the following to convert one of the columns to a vector  but it doesn t work   avector  lt - as vector aframe  a2    class avector    1   data frame    This is the only solution I could come up with  but I m assuming there has to be a better way to do this   class aframe  a2      1   data frame  avector   c   for atmp in aframe  a2      avector  lt - atmp   class avector   1   numeric    Note  My vocabulary above may be off  so please correct me if so   I m still learning the world of R   Additionally  any explanation of what s going on here is appreciated  i e  relating to Python or some other language would help

User · Answer

Another advantage of using the      operator is that it works both with data frame and data table  So if the function has to be made running for both data frame and data table  and you want to extract a column from it as a vector then  data   column name       is best

User · Answer

If you just use the extract operator it will work   By default     sets option drop TRUE  which is what you want here   See      for more details    gt   a1   c 1  2  3  4  5   gt   a2   c 6  7  8  9  10   gt   a3   c 11  12  13  14  15   gt   aframe   data frame a1  a2  a3   gt  aframe   a2    1   6  7  8  9 10  gt  class aframe   a2     1   numeric

User · Answer

You can try something like this-  as vector unlist aframe a2

User · Answer

There s now an easy way to do this using dplyr   dplyr  pull aframe  a2

User · Answer

I use lists to filter dataframes by whether or not they have a value  in  a list    I had been manually creating lists by exporting a 1 column dataframe to Excel where I would add      around each element  before pasting into R  list  lt - c  el1    el2        which was usually followed by FilteredData  lt - subset Data  Column  in  list    After searching stackoverflow and not finding an intuitive way to convert a 1 column dataframe into a list  I am now posting my first ever stackoverflow contribution     assuming you have a 1 column dataframe called  df  list  lt - c   for i in 1 nrow df      list  lt - append list  df i 1     View list    This list is not a dataframe  it is a list of values   You can filter a dataframe using  subset  Data    Column   in  list

User · Answer

We can also convert data frame columns generically to a simple vector  as vector is not enough as it retains the data frame class and structure  so we also have to pull out the first  and only  element   df column object  lt - aframe  2  simple column  lt - df column object  1     All the solutions suggested so far require hardcoding column titles  This makes them non-generic  imagine applying this to function arguments     Alternatively  you could  of course read the column names from the column first and then insert them in the code in the other solutions

User · Answer

as vector unlist aframe  a2

User · Answer

I m going to attempt to explain this without making any mistakes  but I m betting this will attract a clarification or two in the comments   A data frame is a list  When you subset a data frame using the name of a column and    what you re getting is a sublist  or a sub data frame   If you want the actual atomic column  you could use     or somewhat confusingly  to me  you could do aframe  2  which returns a vector  not a sublist   So try running this sequence and maybe things will be clearer   avector  lt - as vector aframe  a2    class avector    avector  lt - aframe   a2    class avector   avector  lt - aframe  2  class avector

User · Answer

You could use   extraction   class aframe a1   1   numeric    or the double square bracket   class aframe   a1      1   numeric

User · Answer

You do not need as vector    but you do need correct indexing  avector  lt - aframe     a2    The one other thing to be aware of is the drop FALSE option to     R gt  aframe  lt - data frame a1 c1 5  a2 6 10  a3 11 15  R gt  aframe   a1 a2 a3 1  1  6 11 2  2  7 12 3  3  8 13 4  4  9 14 5  5 10 15 R gt  avector  lt - aframe    a2   R gt  avector  1   6  7  8  9 10 R gt  avector  lt - aframe    a2   drop FALSE  R gt  avector   a2 1  6 2  7 3  8 4  9 5 10 R gt

User · Answer

a1   c 1  2  3  4  5  a2   c 6  7  8  9  10  a3   c 11  12  13  14  15  aframe   data frame a1  a2  a3  avector  lt - as vector aframe  a2     avector lt -unlist avector   this will return a vector of type  integer

[r] Convert data.frame column to a vector?

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