title: Python Non negative Matrix Factorization that handles both zeros and missing data?
body: <p>I look for a NMF implementation that has a python interface, and handles both missing data and zeros.</p>
  
  <p>I don't want to impute my missing values before starting the factorization, I want them to be ignored in the minimized function.</p>
  
  <p>It seems that neither scikit-learn, nor nimfa, nor graphlab, nor mahout propose such an option.</p>
  
  <p>Thanks!</p>