I have long wondered why the WMF Fundraising department seems stuck on A/B testing instead of multivariate analysis.[1] Does anyone know? In any case, modern multivariate analysis depends on principal component analysis[2] (PCA) and it really does work great. I have been told for years that it is planned and can't wait to see what happens to fundraising when implemented. So the reason why I am writing is because I just noticed that EIGENSOFT[3] version 5 has "a new option for PCA projection with large amounts of missing data" in pca.c[4] which is really clean code, too. I hope this helps. Best regards, James Salsman [1] http://en.wikipedia.org/wiki/Multivariate_analysis [2] http://en.wikipedia.org/wiki/Principal_component_analysis [3] http://www.hsph.harvard.edu/alkes-price/software/ [4] http://www.hsph.harvard.edu/alkes-price/files/2013/08/EIG5.0.1.tar.gz