This blog has two parts. In the first part, I will cover how to use spatial join to see data points within a certain radius from a specific point. In the second part, I will demonstrate how to build a dynamic trade area from a certain location.
Part-1
I’m using the Victorian accidents dataset. Which contains the locations of the accidents across Victoria. The second dataset contains the location of (user) defined points. I’ve joined two datasets by using left outer join. I also calculated the fields on which I’m joining. For left I am using the “Makepoint” function and for right, I am using the ” Buffer & Makepont” function. After creating these calculated fields select “Intersects” from the drop-down option.
Now plot the point-density map using the main dataset (Accidents). Bring the Location into the color mark. It will color all accidents within a 5 Km radius from the defined locations.
I have used Four locations in my example and created a buffer of 5 km from each of the locations to see accidents within that radius.
Part-2
This part of the blog will cover how to build a dynamic trade area from the selected point. To start with I need to create a Set by selecting the accident no. field. For time being select only one accident no. and name it “Location Set”.
Now create a parameter to select Km.
To build a trade area from a certain point I need to create a calculated field. I have used the ‘select km’ parameter in the Trade Area formula so we can select the radius of the area as per our choice.
Now double click the “Trade Area” calculated field. It will plot a circle of 5 km from the point which we have selected while creating the Set. Add a second layer to the map by using the Latitude and Longitude of the accidents and plot point-density map.
The last thing is to plot the trade area around the selected point. For that, I need to create Set Action on a worksheet or dashboard.
All done!
The link to the workbook is as below:
https://public.tableau.com/app/profile/saqib786/viz/SpatialJoinandDynamicTradeArea/SpatialJoin
