如何使用r中的PmmlTransformation设置缺失值

I have a dataframe in r which has some NA values in it. How can I use pmmlTransformations to set a missing value treatment for these fields. Ive seen that you can set missingValue treatments when transforming the data (normalization, field mapping, etc) but I would like to know how to just set the missing values with out having to normalize the data.I have a dataframe in r which has some NA value