These files should be placed in a single folder on the C: drive.
This path needs to be added to the Matlab Search path. to do this
# Open Matlab
# Select File --> Set Path . . .
# This will open a small window. Select Add Folder . . .
# Choose the folder the files are in, and select OK.
# To make this the first folder that Matlab searches for the XrayProject.mat file, use the Set Path Dialog to mvoe the folder to the top of the list