Row names column names in R

Question

Do the following function pairs generate exactly the same results   Pair 1  names    amp  colnames      Pair 2  rownames    amp  row names

User · Answer

And another expansion     create dummy matrix set seed 10  m  lt - matrix round runif 25  1  5    5  d  lt - as data frame m    If you want to assign new column names you can do following on data frame     an identical effect can be achieved with colnames      names d   lt - LETTERS 1 5   gt  d   A B C D E 1 3 2 4 3 4 2 2 2 3 1 3 3 3 2 1 2 4 4 4 3 3 3 2 5 1 3 2 4 3   If you  however run previous command on matrix  you ll mess things up   names m   lt - LETTERS 1 5   gt  m        1    2    3    4    5   1      3    2    4    3    4  2      2    2    3    1    3  3      3    2    1    2    4  4      4    3    3    3    2  5      1    3    2    4    3 attr   names     1   A   B   C   D   E  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA   20  NA  NA  NA  NA  NA  NA    Since matrix can be regarded as two-dimensional vector  you ll assign names only to first five values  you don t want to do that  do you    In this case  you should stick with colnames     So there

User · Answer

Just to expand a little on Dirk s example   It helps to think of a data frame as a list with equal length vectors   That s probably why names works with a data frame but not a matrix   The other useful function is dimnames which returns the names for every dimension   You will notice that the rownames function actually just returns the first element from dimnames   Regarding rownames and row names  I can t tell the difference  although rownames uses dimnames while row names was written outside of R   They both also seem to work with higher dimensional arrays    gt a  lt - array 1 5  1 4   gt  a 1      gt  rownames a   lt -  a   gt  row names a   1   a   gt  a     1  1         1    2  a    1    2   gt  dimnames a    1    1   a     2   NULL    3   NULL    4   NULL

User · Answer

As Oscar Wilde said     Consistency is the last refuge of the   unimaginative    R is more of an evolved rather than designed language  so these things happen  names   and colnames   work on a data frame but names   does not work on a matrix   R gt  DF  lt - data frame foo 1 3  bar LETTERS 1 3   R gt  names DF   1   foo   bar  R gt  colnames DF   1   foo   bar  R gt  M  lt - matrix 1 9  ncol 3  dimnames list 1 3  c  alpha   beta   gamma     R gt  names M  NULL R gt  colnames M   1   alpha   beta    gamma  R gt

User · Answer

I think that using colnames and rownames makes the most sense  here s why   Using names has several disadvantages   You have to remember that it means  column names   and it only works with data frame  so you ll need to call colnames whenever you use matrices  By calling colnames  you only have to remember one function   Finally  if you look at the code for colnames  you will see that it calls names in the case of a data frame anyway  so the output is identical   rownames and row names return the same values for data frame and matrices  the only difference that I have spotted is that where there aren t any names  rownames will print  NULL   as does colnames   but row names returns it invisibly   Since there isn t much to choose between the two functions  rownames wins on the grounds of aesthetics  since it pairs more prettily withcolnames    Also  for the lazy programmer  you save a character of typing

[r] Row names & column names in R

Examples related to r

Examples related to columnname

Examples related to rowname