source: sasview/src/sas/sasgui/perspectives/pr/media/pr_help.rst @ 3bb1090

ESS_GUIESS_GUI_DocsESS_GUI_batch_fittingESS_GUI_bumps_abstractionESS_GUI_iss1116ESS_GUI_iss879ESS_GUI_iss959ESS_GUI_openclESS_GUI_orderingESS_GUI_sync_sascalccostrafo411magnetic_scattrelease-4.1.1release-4.1.2release-4.2.2release_4.0.1ticket-1009ticket-1094-headlessticket-1242-2d-resolutionticket-1243ticket-1249ticket885unittest-saveload
Last change on this file since 3bb1090 was d85c194, checked in by Piotr Rozyczko <piotr.rozyczko@…>, 7 years ago

Remaining modules refactored

  • Property mode set to 100644
File size: 1.9 KB
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[ec392464]1.. pr_help.rst
2
3.. This is a port of the original SasView html help file to ReSTructured text
4.. by S King, ISIS, during SasView CodeCamp-III in Feb 2015.
5
6.. |pi| unicode:: U+03C0
[8a22b5b]7.. |bigphi| unicode:: U+03A6
8.. |bigsigma| unicode:: U+03A3
[ec392464]9.. |chi| unicode:: U+03C7
10
11P(r) Inversion Perspective
12==========================
13
[8a22b5b]14Description
15-----------
[ec392464]16
[8a22b5b]17This tool calculates a real-space distance distribution function, *P(r)*, using
18the inversion approach (Moore, 1908).
19
20*P(r)* is set to be equal to an expansion of base functions of the type
21
22  |bigphi|\_n(r) = 2.r.sin(|pi|\ .n.r/D_max)
[ec392464]23
24The coefficient of each base function in the expansion is found by performing
[8a22b5b]25a least square fit with the following fit function
26
27  |chi|\ :sup:`2` = |bigsigma|\ :sub:`i` [ I\ :sub:`meas`\ (Q\ :sub:`i`\ ) - I\ :sub:`th`\ (Q\ :sub:`i`\ ) ] :sup:`2` / (Error) :sup:`2` + Reg_term
[ec392464]28
[8a22b5b]29where I\ :sub:`meas`\ (Q) is the measured scattering intensity and
30I\ :sub:`th`\ (Q) is the prediction from the Fourier transform of the *P(r)* 
31expansion.
[ec392464]32
[8a22b5b]33The *Reg_term* term is a regularization term set to the second derivative
34d\ :sup:`2`\ *P(r)* / dr\ :sup:`2` integrated over *r*. It is used to produce a
35smooth *P(r)* output.
[ec392464]36
[8a22b5b]37.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
[ec392464]38
[a9dc4eb]39Using the perspective
40---------------------
[ec392464]41
[8a22b5b]42The user must enter
43
44*  *Number of terms*: the number of base functions in the P(r) expansion.
[ec392464]45   
[8a22b5b]46*  *Regularization constant*: a multiplicative constant to set the size of
[ec392464]47   the regularization term.
48
[8a22b5b]49*  *Maximum distance*: the maximum distance between any two points in the
[ec392464]50   system.
[8a22b5b]51
52.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
53
54Reference
55---------
56
57P.B. Moore
58*J. Appl. Cryst.*, 13 (1980) 168-175
59
60.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
61
[a9dc4eb]62.. note::  This help document was last changed by Steve King, 01May2015
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