How to impute the missing data with the most frequent value

I have a dataset containing categorical and numerical data and I would like to know how I can impute the missing data with the frequent value.
For example
ID         Feature1      Feature 2        Feature 3 
_______________________________________
123      core i7          Windows         33844690
334       IOS              phone             99983648

Note that the missing values are huge but I can't drop the column.
Is there an operator I can use for nominal data to be replaced with the mode? and the numerical data with average or max?