1 Reply Latest reply on Mar 8, 2016 3:39 PM by Patrick Van Der Hyde

    Calculated Field Assistance

    Tyrone Sterling



      I am doing an analysis on our current vehicle usage. We are currently using 3 vehicles (though we have data going back to when we were using 4). The data dates back to FY2014 (fiscal year starts in October). One of the main purposes of this analysis is to determine if our numbers of uses validate or need for 3 vehicles, and if not what would be in the necessary increase in usage in order to meet the validation level. Factors including in this extrapolation is the projected increase in staff leading to a pre-determined 10% increase to our most traveled destination (campus). Based on the 10% increase to campus compared to the overall usage, that percentage was in determining how many annual trips would be necessary in the future based on federal business days and number of projected future staff. The numbers used for the 3-car justification specifically, were derived from FY2015's numbers. Attached is the data source, there is a sheet detailing the breakdown of the aforementioned justification requirements as well as the tracking log's raw data (used as the data source). The .twb is also included. I am looking to have calculated field for the 3-car justification based on the details given, but I'm not sure how to effectively add information from the second sheet of the data source in order to create calculated fields such as: annual increase of vehicle usage needed to justify a certain number of vehicles, trips per future employee, per year in order to justify a certain number of vehicles, etc. I hope that I am giving helpful details as to what it is I need assistance with.





        • 1. Re: Calculated Field Assistance
          Patrick Van Der Hyde

          Hello Tyrone,


          I am a Tableau employee today, in part, because of similar sorts of analysis related to vehicles.    I just looked at the data and did a bit of analysis that I think is based on common sense.  Looking at a view that counts trips by week or month and comparing to the current FY2016 trends, the usage of the cars is down considerably. 


          From a destination perspective,  6610 is no longer getting any trips (since April of 2015) and the campus trips are experiencing a downward trend (although Feb data appears incomplete and March data is not collected yet).   


          Here is a year over year view with Count of ID (trips) on the rows shelf. 



          That said, my qualification for need would be based on how often all the vehicles were in use for a given time period.  I created a view that groups Year, Week, Day, and Hour on a Bar chart to show the count of ID's (trips) initiated in the same hour.  In all 3 fiscal years, there are only 2 occasions where all three vehicles were in use. 


          Maybe that isn't helpful but that's the sort of methodology I would use to determine need..  I would base it on availability of vehicles vs demand.