Using Dual Display and the Add/Subtract routine.
Dual Display allows 2 spectra to be displayed simultaneously. They are scaled together and Zoom expansion applies to both.
The Add/Subtract subroutine allows 2 spectra to be added together or subtracted, and the result becomes the current spectrum.
To display more than 2 spectra, create a 2D data set containing the desired files, and use a stacked plot.
Note that these features are not included in NUTS Lite.
Open the first spectrum to be compared.
Select Load AS buffer from the Tools/Add Subtract Routine menu, or type AL.
This places a copy of the current spectrum into the Add/Subtract buffer.
Open the second spectrum to be compared.
The contents of the buffer can be displayed above the current spectrum by selecting Dual Display from the View menu, from the Tools menu or by typing DD. The buffer is shown in green.
The DD command is a toggle, so executing it again will turn off display of the buffer spectrum. The data remains in the buffer, however.
Use Zoom to expand the two spectra together.
Use the right hand scroll bar, Page Up/Down keys or < > keys to scale the spectra vertically.
Use the scroll bar at the bottom of the screen to pan both spectra.
Use the AM command to
- Enter a scaling factor for the buffer spectrum
- Enter a horizontal offset, for use in cases where the spectra do not line up exactly
- Change the vertical position of the buffer spectrum
The Add/Subtract subroutine provides more options than the Dual Display mode.
Enter the subroutine from the Tools menu, or by typing AS.
Once in the subroutine, you can change the buffer spectrum’s multiplier, horizontal offset and vertical position from the Edit menu, (just as was done with the AM command above).
It is also possible to shift the buffer spectrum horizontally using the left and right cursor arrow keys. Each key click moves the buffer spectrum one point. Holding down the shift key and using the same cursor keys moves the spectrum 10 points at a time.
From the Display menu, you can choose to display the difference (current spectrum minus buffer spectrum). This is the most convenient way to make adjustments to the vertical scale and horizontal offset to match the 2 spectra for good subtraction.
Choosing Both from the Display menu reverts to display of the buffer spectrum in green, instead of the difference.
Once all desired adjustments have been made, select Add or Subtract from the Edit menu to replace the current spectrum with the sum or difference (current minus buffer). Either operation can be undone while still in the AS routine by performing the opposite operation.
Once addition or subtraction has been executed and the routine exited (with <Enter>), the current data set has been replaced by the sum or difference.
Last updated: 11/3/97.