How to Find Difference Between two Columns

Hello,
 
Thank you for writing to us.
 
The desired output can be achieved in the following way:
 
1. Reorganize the data
 
We kindly advise organizing the CSV data in the following manner: 
 
Create a column representing every month containing the corresponding value. For example, instead of:

CONTRACT_NUMBER, YEAR, MONTH, VALUE
H0524, 2014, January, 93
H0524, 2014, February, 59

   organize the data in the following way:

CONTRACT_NUMBER, YEAR, January, February
H0524, 2014, 93, 0
H0524, 2014, 0, 59

 
If using a JSON data source it is possible to manipulate the JSON data to achieve the same desired output. This is illustrated in the JSFiddle example.
 
2. Use calculated measure
 
    Create a calculated measure which will display the difference between January and February:

{
  uniqueName: "Difference of Jan & Feb",
  formula: "sum(\"January\") - sum(\"February\")",
  caption: "Difference of Jan & Feb"
}

 
Here is a JSFiddle example for illustration.
 
Please let us know if this works fine for you.
 
Best Regards,
Vera

Hello,
 
Thank you for your reply.
 
Please consider the following approach (without restructuring the CSV data):
 
The Difference aggregation can be used, however, only the difference between the columns will be displayed. 
 
Here is a JSFiddle example for illustration.
Please note that this should work for CSV data as well.
 
Would such an approach work for your case?
 
We are looking forward to hearing from you.
 
Best Regards,
Vera