Assume a data set with multiple columns, where the categorical data are coded. What is the best rule(s) or rule of thumb to determine whether each column contains qualitative data or quantitative data?
One possible way is to count the number of unique values and if the unique value count is less than some threshold value, then treat it as qualitative. But as this can differ with the size of data (i.e. for big data), is there a particular method to decide on the threshold?
Or is there any other completely different approach to this?