Changeset d7af1c6 in sasmodels

Timestamp:

Jun 12, 2018 6:01:29 AM (6 years ago)

Author:

Adam Washington <adam.washington@…>

Branches:

master

Children:

ac995be

Parents:

02e3c54

Message:

First attempt at log spaced sesans

Files:

• doc/guide/sesans/sans_to_sesans.rst (modified) (1 diff)
• sasmodels/sesans.py (modified) (2 diffs)

doc/guide/sesans/sans_to_sesans.rst

@@ -68 +68 @@
 .. math:: H_{nm} = \frac{2 \pi}{\delta_m}
           (q_n J_1(q_n \delta_m) - q_{n-1} J_1(q_{n-1} \delta_m))
+
+Also not that, for the limit as :math:`\delta_m` approaches zero,
+
+.. math:: G(0)
+          =
+          \sum_{n=0} \pi \frac{d \Sigma}{d \Omega} (q_n) (q_n^2 - q_{n-1}^2)

sasmodels/sesans.py

@@ -14 +14 @@
 import numpy as np  # type: ignore
 from numpy import pi  # type: ignore
-from scipy.special import j0
+from scipy.special import j0, j1
+
 
 class SesansTransform(object):
@@ -59 +60 @@
         SElength = np.asarray(SElength, dtype='float32')
 
-        #Rmax = #value in text box somewhere in FitPage?
+        # Rmax = #value in text box somewhere in FitPage?
         q_max = 2*pi / (SElength[1] - SElength[0])
         q_min = 0.1 * 2*pi / (np.size(SElength) * SElength[-1])
-        q = np.arange(q_min, q_max, q_min, dtype='float32')
-        dq = q_min
+        # q = np.arange(q_min, q_max, q_min, dtype='float32')
+        q = np.exp(np.arange(np.log(q_min), np.log(q_max), np.log(2),
+                             dtype=np.float32))
+        q = np.hstack([0], q)
 
-        H0 = np.float32(dq/(2*pi)) * q
+        H0 = np.pi * (q[1:]**2 - q[-1]**2)
 
         # repq = np.tile(q, (SElength.size, 1)).T
         H = np.outer(q, SElength)
-        j0(H, out=H)
-        H *= np.float32(dq/(2*pi))
-        H *= q.reshape((-1, 1))
+        j1(H, out=H)
+        H *= q
+        H = H[1:] - H[:-1]
+        H *= 2 * np.pi / SElength
 
         lam = np.asarray(lam, dtype=np.float32)