Changes between Initial Version and Version 1 of Ticket #1102, comment 5


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Timestamp:
May 29, 2018 1:41:06 PM (7 years ago)
Author:
pkienzle
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  • Ticket #1102, comment 5

    initial v1  
    11 
    22IGOR macros appear to compute using 20-point gaussian quadrature within [q-3dq, q+3dq].   For broad resolution functions, the lower bound is first set to zero (the quadrature points range within [-0.9931, 0.9931] rather than [-1, 1] so the lowest q point evaluated is never actually zero).  Strangely, the high q side is not similarly truncated, so the gaussian quadrature points will be in [0, q+3dq], with the center at (q+3dq)/2 rather than q. 
     3 
     4Given a constant dq/q, the lowest q point grows like  
     5{{{ 
     6   ((-0.9931)*(q+3dq) + q+3dq)/2 ~= 0.0086*q for 50% dq/q 
     7}}} 
     8This is presumably why the slope is preserved in IGOR, since unlike SasView, higher q points are not all pulling from the same low q cutoff. 
    39 
    410Source: