Convert data frame column format from character to factor

Question

I would like to change the format  class  of some columns of my data frame object  mydf  from charactor to factor   I don t want to do this when I m reading the text file by read table   function   Any help would be appreciated

User · Answer

Another short way you could use is a pipe    lt  gt    from the magrittr package  It converts the character column mycolumn to a factor   library magrittr   mydf mycolumn   lt  gt   factor

User · Answer

If you want to change all character variables in your data frame to factors after you ve already loaded your data  you can do it like this  to a data frame called dat     character vars  lt - lapply dat  class      character  dat   character vars   lt - lapply dat   character vars   as factor    This creates a vector identifying which columns are of class character  then applies as factor to those columns   Sample data   dat  lt - data frame var1   c  a    b                      var2   c  hi    low                      var3   c 0  0 1                     stringsAsFactors   FALSE

User · Answer

Hi welcome to the world of R   mtcars   look at this built in data set str mtcars   allows you to see the classes of the variables  all numeric    one approach it to index with the   sign and the as factor function mtcars am  lt - as factor mtcars am   another approach mtcars    cyl    lt - as factor mtcars    cyl    str mtcars     now look at the classes   This also works for character  dates  integers and other classes  Since you re new to R I d suggest you have a look at these two websites   R reference manuals  http   cran r-project org manuals html  R Reference card  http   cran r-project org doc contrib Short-refcard pdf

User · Answer

To do it for all names df    lt - lapply  df  factor    the  quot    quot  keeps the dataframe structure  col names  lt - names df    to do it for some names in a vector named  col names  df col names   lt - lapply df col names    factor   Explanation  All dataframes are lists and the results of   used with multiple valued arguments are likewise lists  so looping over lists is the task of lapply  The above assignment will create a set of lists that the function data frame   lt - should successfully stick back into into the dataframe  df Another strategy would be to convert only those columns where the number of unique items is less than some criterion  let s say fewer than the log of the number of rows as an example  cols to factor  lt - sapply  df  function col  length unique col    lt  log10 length col     df  cols to factor   lt - lapply df  cols to factor    factor

User · Answer

Unless you need to identify the columns automatically  I found this to be the simplest solution  df name  lt - as factor df name   This makes column name in dataframe df a factor

User · Answer

I ve doing it with a function  In this case I will only transform character variables to factor   for  i in 1 ncol data        if is character data  i             data  i  factor data  i

User · Answer

You could use dplyr  mutate if   to convert all character columns or dplyr  mutate at   for select named character columns to factors   library dplyr     all character columns to factor  df  lt - mutate if df  is character  as factor     select character columns  char1    char2   etc  to factor  df  lt - mutate at df  vars char1  char2   as factor

[r] Convert data.frame column format from character to factor

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