Changeset 78f02c3 in sasview for src/sas/invariant/media/pr_help.rst

Timestamp:

Feb 14, 2015 10:12:40 AM (9 years ago)

Author:

smk78

Branches:

master, ESS_GUI, ESS_GUI_Docs, ESS_GUI_batch_fitting, ESS_GUI_bumps_abstraction, ESS_GUI_iss1116, ESS_GUI_iss879, ESS_GUI_iss959, ESS_GUI_opencl, ESS_GUI_ordering, ESS_GUI_sync_sascalc, costrafo411, magnetic_scatt, release-4.1.1, release-4.1.2, release-4.2.2, release_4.0.1, ticket-1009, ticket-1094-headless, ticket-1242-2d-resolution, ticket-1243, ticket-1249, ticket885, unittest-saveload

Children:

898a8b9

Parents:

3e2ebbb

Message:

Level 1 sphinx-ready commit of remaining help files

File:

• src/sas/invariant/media/pr_help.rst (modified) (1 diff)

src/sas/invariant/media/pr_help.rst

@@ -1 +1 @@
 ..pr_help.rst
+
+.. This is a port of the original SasView html help file to ReSTructured text
+.. by S King, ISIS, during SasView CodeCamp-III in Feb 2015.
 
 P(r) Inversion Perspective
 ==========================
 
-Placeholder for P(r) help
+The inversion approach is based on Moore, J. Appl. Cryst., (1980) 13, 168-175.
+
+P(r) is set to be equal to an expansion of base functions  of the type 
+phi_n(r) = 2*r*sin(pi*n*r/D_max).
+
+The coefficient of each base function in the expansion is found by performing 
+a least square fit with the following fit function:
+
+chi**2 = sum_i[ I_meas(q_i) - I_th(q_i) ]**2/error**2 + Reg_term
+
+where I_meas(q) is the measured scattering intensity and I_th(q) is the 
+prediction from the Fourier transform of the P(r) expansion. 
+
+The Reg_term term is a regularization term set to the second derivative 
+d**2P(r)/dr**2 integrated over r. It is used to produce a smooth P(r) output.
+
+The following are user inputs:
+
+   - Number of terms: the number of base functions in the P(r) expansion. 
+   
+   - Regularization constant: a multiplicative constant to set the size of 
+the regularization term.
+
+   - Maximum distance: the maximum distance between any two points in the 
+   system.