comparand in a sentence

1. In this method, the subpixel peak location is approximated by a simple formula involving peak pixel value and the values of its nearest neighbors, where r _ { ( 0, 0 ) } is the peak value and r _ { ( 1, 0 ) } is the nearest neighbor in the x direction ( assuming, as in most approaches, that the integer shift has already been found and the comparand images differ only by a subpixel shift ).
2. It's difficult to find comparand in a sentence.