arules package (apriori)

hello,
I want to perform the Apriori association rules algorithm to my data. The set of data contains missing values and consists in a combination of continuous and categorical variables.
After discretizing the continuous variables, I wrote the following instruiction to perform Apriori, but I obtained the following error message:

rules <- apriori(dd_new,parameter=list(supp=0.5, conf=0.9, target="rules"))

Erreur dans asMethod(object) : 
  column(s)12345679101112131415162123242553not a factor

Does this have any relation with the missing values?

Thanks.

Cordially,

Soumaya