Changing factor levels with dplyr mutate

Question

This is probably simple and I feel stupid for asking  I want to change the levels of a factor in a data frame  using mutate  Simple example   library  dplyr   dat  lt - data frame x   factor  A    y   1  mutate dat levels x     B     I get   Error  Unexpected     in  mutate dat levels x       Why is this not working  How can I change factor levels with mutate

User · Answer

I m not quite sure I understand your question properly  but if you want to change the factor levels of cyl with mutate   you could do   df  lt - mtcars   gt   mutate cyl   factor cyl  levels   c 4  6  8      You would get     gt  str df cyl    Factor w  3 levels  4   6   8   2 2 1 2 3 2 3 1 1 2

User · Answer

With the forcats package from the tidyverse this is easy  too   mutate dat  x   fct recode x   B     A

User · Answer

You can use the recode function from dplyr   df  lt - iris   gt        mutate Species   recode Species  setosa    SETOSA            versicolor    VERSICOLOR            virginica    VIRGINICA

User · Answer

Maybe you are looking for this plyr  revalue function   mutate dat  x   revalue x  c  A     B       You can see plyr  mapvalues too

User · Answer

From my understanding  the currently accepted answer only changes the order of the factor levels  not the actual labels  i e   how the levels of the factor are called   To illustrate the difference between levels and labels  consider the following example    Turn cyl into factor  specifying levels would not be necessary as they are coded in alphanumeric order        mtcars2  lt - mtcars   gt   mutate cyl   factor cyl  levels   c 4  6  8         mtcars2 cyl 1 5        1  6 6 4 6 8      Levels  4 6 8   Change the order of levels  but not the labels itself  cyl is still the same column       mtcars3  lt - mtcars2   gt   mutate cyl   factor cyl  levels   c 8  6  4         mtcars3 cyl 1 5        1  6 6 4 6 8      Levels  8 6 4     all mtcars3 cyl  mtcars2 cyl        1  TRUE   Assign new labels to cyl  The order of the labels was  c 8  6  4   hence we specify new labels as follows       mtcars4  lt - mtcars3   gt   mutate cyl   factor cyl  labels   c  new value for 8                                                                    new value for 6                                                                    new value for 4          mtcars4 cyl 1 5        1  new value for 6 new value for 6 new value for 4 new value for 6 new value for 8      Levels  new value for 8 new value for 6 new value for 4   Note how this column differs from our first columns       all as character mtcars4 cyl   mtcars3 cyl         1  TRUE       Note  TRUE here indicates that all values are unequal because I used    instead of         as character   was required as the levels were numeric and thus not comparable to a character vector     More details   If we were to change the levels of cyl using mtcars2 instead of mtcars3  we would need to specify the labels differently to get the same result  The order of labels for mtcars2 was  c 4  6  8   hence we specify new labels as follows       change labels of mtcars2  order used to be  c 4  6  8      mtcars5  lt - mtcars2   gt   mutate cyl   factor cyl  labels   c  new value for 4                                                                    new value for 6                                                                    new value for 8        Unlike mtcars3 cyl and mtcars4 cyl  the labels of mtcars4 cyl and mtcars5 cyl are thus identical  even though their levels have a different order        mtcars4 cyl 1 5        1  new value for 6 new value for 6 new value for 4 new value for 6 new value for 8      Levels  new value for 8 new value for 6 new value for 4      mtcars5 cyl 1 5        1  new value for 6 new value for 6 new value for 4 new value for 6 new value for 8      Levels  new value for 4 new value for 6 new value for 8      all mtcars4 cyl  mtcars5 cyl        1  TRUE      levels mtcars4 cyl     levels mtcars5 cyl       1  FALSE  TRUE FALSE

User · Answer

Can t comment because I don t have enough reputation points  but recode only works on a vector  so the above code in  Stefano s answer should be  df  lt - iris   gt     mutate Species   recode Species        setosa    SETOSA        versicolor    VERSICOLOR        virginica    VIRGINICA

[r] Changing factor levels with dplyr mutate

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