A Treatise on the ALL() Function in DAX – or – ‘Is it all er nuthin’ with you?’
With all the hubbub surrounding PowerPivot, I have been given the task of learning DAX: not an easy task when the product is still pre-release and there aren’t any step-by-step books on hand! With a list of functions and a vague understanding of how they work, plus powerpivotpro’s very helpful posts, I decided to set myself a problem that I could hopefully solve with DAX. I noticed that in the long list of DAX functions, standard deviation and correlation were missing. As I have had to use these fairly frequently in MDX (along with various derivations of such), I decided I would try to set up a correlation measure in a powerpivot pivot table. In the process, I discovered some interesting nuances to DAX, one of which is the topic of this blog post. It should be fun for ALL()!