Converting data frame column from character to numeric

Question

I have a data frame that I construct as such    gt  yyz  lt - data frame a   c  1   2   n a    b   c 1 2  n a      gt  apply yyz  2  class        a           b   character   character    I am attempting to convert the last column to numeric while still maintaining the first column as a character   I tried this    gt  yyz b  lt - as numeric as character yyz b    gt  yyz   a  b   1  1   2  2   n a NA   But when I run the apply class it is showing me that they are both character classes    gt  apply yyz  2  class        a           b   character   character    Am I setting up the data frame wrong  Or is it the way R is interpreting the data frame

User · Accepted Answer

If we need only one column to be numeric  yyz b  lt - as numeric as character yyz b     But  if all the columns needs to changed to numeric  use lapply to loop over the columns and convert to numeric by first converting it to character class as the columns were factor   yyz    lt - lapply yyz  function x  as numeric as character x      Both the columns in the OP s post are factor because of the string  n a    This could be easily avoided while reading the file using na strings    n a  in the read table read csv or if we are using data frame  we can have character columns with stringsAsFactors FALSE  the default is stringsAsFactors TRUE     Regarding the usage of apply  it converts the dataset to matrix and matrix can hold only a single class   To check the class  we need  lapply yyz  class    Or  sapply yyz  class    Or check  str yyz

[r] Converting data frame column from character to numeric

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