
In order to perform a subtraction of a foreground and background measurement multiple requirements must be satisfied. Currently, the two files must have identical:
- A3 scan points (also direction)
- 2&theta;
- Ei
- Scan Parameters
- type (raw or converted)

If any of these are not met for any of the data files, the two datasets cannot be subtracted. In the subtraction window, any unsatisfied requirements are signified with a red background of the affected datafile(s) for both the foreground and bacground datasets. Selecting such a datafile shows it properties to the left (foreground) or right (background) with a red highlight background. 

If the loaded datafiles have been measured with identical instrumental parameters, it might happend that the loading sequence of them differs. This can be corrected by drag-and-dropping the files into the correct order, either directly in the subtraction window or in the  datafile overview of the main interface.

It is possible to subtract dataset with different monitor values. MJOLNIR rescales the background datafiles by the ratio between the measured foreground and background. However, uncertainties are not propagated! 

Parameters are equal if they have difference less than (Absolute tolerance):
A3: 0.1 deg
2&theta;: 0.1 deg
Ei: 0.1 meV