Russel responded with the following via email:
In general Tableau does do forecasting:
However I do not believe it is very robust, so a lot of people probably leverage R/SAS/SPSS to build their models. It doesn't sound like you have a very complex model so Tableau might fit your needs.
To be able to filter by the dimensions you are describing you'll need to create a more granular model. For example: If I create a Monthly Forecast, I can show numbers via. Months/Quarter/or Year, however I lack the ability to do Days (I lack the granularity in my model, I cannot drill down). The trick is to figure out the most granular level of data you have and build the model from there, that way you can roll up to all the views you want. So maybe I create a Hourly forecast, I can roll-up hours to Days->Weeks->Months->etc. Depending on the amount of data you have, that could be a wise decision or a bad decision (how much confidence do you place in your data, as you get more granular the amount of data in each forecast is smaller).
I have the data by all the dimensions - sales person, brand, product (3 levels), property, date (both insertion and delivery), company, etc. I guess our challenge is how to do the calculations. I'm struggling putting them together in Tableau, not because the calculation itself is hard if I just wrote it down, but the logic because I'm not familiar with SQL, etc. On the other hand, our IT director said we wouldn't be able to do the calculations outside of Tableau because they would have to be done for every possible permutation to allow Tableau to filter on them. He thought we would have to cube our data, which our developers are not experience with.
Anyway, I'll be interested to meet everyone at the next meeting. Hopefully I'll be in town as I travel a lot.
Awesome, if you can share a sample of the data, please mask any information and it doesn't have to be all the dimensions, that'll be great.
I'll be happy to help try and build the forecast with you. If the calculation is just % of Sales from Previous year (on the given current day) compared to % of Sales so far this year (on the current day), then that shouldn't be too difficult. If its something different please send me the details, or even send me an excel sheet with the formula you are using. You can post it, or send it directly to my email account (listed on the event pages).
I can help to either code solutions in SQL or Tableau (and I can help build cubes in SSAS), either way the calculation has to take place somewhere at some point in time. If you want it down to each unique value of your dimensions, then the price to pay is the amount of calculations that need to take place to provide that granularity. With that said a lot of people either aggregate values and create buckets of data or remove any variables that do not influence the model or only reduce their models down to where it makes sense (having only 100K records to model with using 1K variables isn't great, having 100M records with 1K variables is better (but it all depends)). If you can calculate the number of unique values per dimension and multiple them together that'll help me understand the amount of data we are talking about.
If you want to wait till the next event that is okay too and I'll be happy to talk before or after the event.