May i know the way to remove all '??' in these column??

Coldlen

BalazsBaranyRM

Hi,

the ?s are missing values. How did you get this result? It seems like the output of a full outer join. 

The basic operations for handling missing values are:

• Filter Examples with non-missing rows (if you only have a few missings)
• Select Attributes for removing the affected attribute(s) (if you have many missings and the attribute is not important)
• Replace Missing Values (if you know a replacement value or a reasonable function)
• Impute Missing Values (which builds a model from examples that don't have missing values to predict the missing ones)

In your case, neither seems appropriate. Depending on how you got your example set, you might want to review that process.

Regards,
Balázs