How to convert list given in a data frame to factor/numbers in R Data frame?

Question

mydf is for reproducible purpose . I have mydf data frame , and I want to convert list as factors in mydf , but it throws an error

mydf<-data.frame(col1=c("a","b"),col2=c("f","j"))
mydf$col1<-as.list(mydf$col1)
mydf$col2<-as.list(mydf$col2)
str(mydf)

This is the error I get when I try to change lists to factors/numeric type

mydf$col1<-as.factor(mydf$col1)

Error in order(y) : unimplemented type 'list' in 'orderVector1'

I want my data frame (mydf) to be expected_df (no lists data frame)

expected_df<-data.frame(col1=c("a","b"),col2=c("f","j"))
str(expected_df)

If you compared str(mydf) and str(expected_df) , there is a difference as I am unable to change lists to factors in mydf data frame. Is there any workaround to solve my issue ?

str(mydf)
'data.frame':   2 obs. of  2 variables:
$ col1:List of 2
..$ : Factor w/ 2 levels "a","b": 1
..$ : Factor w/ 2 levels "a","b": 2
$ col2:List of 2
..$ : Factor w/ 2 levels "f","j": 1
..$ : Factor w/ 2 levels "f","j": 2



str(expected_df)
'data.frame':   2 obs. of  2 variables:
$ col1: Factor w/ 2 levels "a","b": 1 2
$ col2: Factor w/ 2 levels "f","j": 1 2

Answer 1

You can use stringsAsFactors = TRUE

> mydf <- data.frame(col1 = c("a", "b"), col2 = c("f", "j"), stringsAsFactors = TRUE)
> mydf
  col1 col2
1    a    f
2    b    j
> mydf$col1
[1] a b
Levels: a b
> str(mydf)
'data.frame':   2 obs. of  2 variables:
$ col1: Factor w/ 2 levels "a","b": 1 2
$ col2: Factor w/ 2 levels "f","j": 1 2

Answer 2

Late to the party here, but I thought I would share my experience for future searches. I was also having the 'Error in order(y)' error when trying to convert a column to factors. The way I got round it was to explicitly label the factors. In your example it would be like so:

# instead of this:
# mydf$col1 <- as.factor(mydf$col1)

# using this:
mydf$col1 <- factor(mydf$col1, levels=c("a","b"))