Using the Difference Method

The difference method is located under Methods -> Difference, and this tool provides the easiest way to create a difference dataset.  You can also follow directions here to create difference datasets using the "Derive new dataset" option from the Tools menu, or from the menu that pops up when you right-click on a geography.

How to create a difference dataset starting with two different datasets:

In the dialog box below we demonstrate how to create a difference dataset for the State Economic Areas (SEA) geography.  Here we intend to subtract the lung cancer rate for white females in 1990 from the rate for white males in the same year (both datasets must be in the same geography; note that if you want to create a difference dataset across all times, you need to use the "Derive new dataset" approach).  At the bottom of the dialog, we have modified the default output name slightly by adding the years of the data that we used in the calculation.

 

Next, click the Run method bar to review the analysis (on the next tab of the task manager), and then click "Run."  The run will produce a new dataset with the name "SEA: RWM90 - SEA: RWF90" that will appear under SEA in the Data View.  You can right click on the dataset, which will give you the options of adding it to a map, or renaming, etc.

Once the new dataset appears in the data view, you can view it in the table (excerpted below), or with any of the other visualization tools.  Note that in a project with multiple times, you need to be careful about the timeslider in the table if you want to be able to see your results.  In the example shown above, we have data only for 1990.  Note that another difference dataset (from the calculation described below) shows only dashes for "no data" in 1990 (results for this set would be visible with the time set at 1980, the year for the first dataset--see below).  In the male/female example, the dataset for males was entered as Input dataset 1, so that values for females were subtracted from males.  Doing the analysis with datasets in the reverse order would give the same results, except for the sign of the difference would be reversed.  

How to create a difference dataset for two times in the same dataset:

In the dialog box below we demonstrate how to create a difference dataset for the same geography (SEAs), where we have subtracted the lung cancer rate for white males in 1960 from the rate in 1980.  At the bottom, we have modified the default output name slightly by adding the years of the data that we used in the calculation.  The final dialog box for subtracting the cancer rate for white males (RWM) in 1960 from the rate for white males in 1980 would look like the image above, and once you click Ok, a new dataset with the name RWM1980-RWM1960" would appear under SEA in the Data View (see the image above).

To map these results (shown here), right click on the dataset (the location of the difference dataset, under SEA in the Data View, is shown in the image above), and select "add to map".