I’ve seen an example of how to create a cohort viz here: http://demo.redash.io/queries/67#table
But what i think weird is how day_number = 0 in table is considered as 1 in cohort visualization.
Take a look at first row in table where DATE = 30/01/2014 and DAY_NUMBER = 0 and VALUE = 40832 and TOTAL = 53141. If you do this calculation VALUE/TOTAL then the result is 0.76837 which is the same with day_number 1 and the same date in cohort (76.84%).
I think this could be misleading for some people.