title: Azure machine learning - data set contains NA but it is not showing as missing value
body: <p>I am new to azure machine learning, I am working on house price prediction data set.
  This data set contain NA values in multiple columns both numeric and categorical but when I am trying to clean it, it is not getting cleaned, because azure is not considering it as missing value. Please let me know how to treat NA missing values.</p>
  <p><strong>What I tried :</strong>
  i tried 'convert dataset' to replace NA with 0 but it is replacing all NA's in categorical as well as numeric columns which i don't want. I want to replace NA in numeric column with only mean not 0.</p>
  <p><strong>What I want</strong> : I want to replace NA in categorical columns with 'Not available' string and in numeric columns with mean.</p>