Running sum on aggregated transactional data That’s grouping a running sum.here’s a link to the running sum daily data.tflx packaged flow. Walking through the steps from above, here’s the entire flow: If necessary add a Clean step to validate. For example in Superstore Sales that is at the level of individual transaction if we want to do a monthly running sum then we’d need to aggregate to the level of Month first.Īdd a Clean step to prepare for the self-join.Īdd a Join step as a non-equi-join with any grouping/partitioning fields in the running sum.Īdd an Aggregate step with any grouping/partitioning fields in the group by to create the running sum. If need be aggregate your data to the desired level. Here’s are the core steps for building this in Tableau Prep: With this principle in mind we can do lookups, difference from prior, moving averages, and so on. The basic principle here is that although Prep doesn’t do row-by-row operations (except for the ranking functions, as of May 2020) what we can do is self-join the data to give each original row of data additional row(s) of data to simulate row-by-row operations using aggregations and/or calculated fields. On the left is the displayed chart of cumulative daily tests that looks great, but the actual daily tests tells a very different picture. Here’s an example from a US COVID-19 press conference in early April 2020. If you’re looking to show trends of a number then running sums are not particularly useful because the running sum is accumulating…with a measure like “# of tests” the running sum is always going to stay level or go up (the only reason to go down would be if there was mis-reported data). running sums) that some users require, and in looking around the internets there wasn’t a purpose-built how-to for running sums in Tableau Prep so here’s one! Using running sums or cumulative totals: A COVID-19 caution Tableau Prep doesn’t (as of May 2020) do all the table calculations that Tableau Desktop can do, but we can teach it to! As part of supporting Tableau’s COVID-19 response Anya A’Hearn and I were using Tableau Prep to work with a new data set that had daily counts but not the cumulative totals (i.e.
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