Changeset 65fbf7c in sasmodels

Timestamp:

May 21, 2018 3:33:49 PM (6 years ago)

Author:

Paul Kienzle <pkienzle@…>

Branches:

master, core_shell_microgels, magnetic_model, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests

Children:

2b2d431

Parents:

87964ac

Message:

play with resolution defined by fixed dtheta,dlambda

Location:

sasmodels

Files:

• compare.py (modified) (2 diffs)
• data.py (modified) (3 diffs)

sasmodels/compare.py

@@ -667 +667 @@
         if opts['zero']:
             q = np.hstack((0, q))
-        data = empty_data1D(q, resolution=res)
+        # TODO: provide command line control of lambda and Delta lambda/lambda
+        #L, dLoL = 5, 0.14/np.sqrt(6)  # wavelength and 14% triangular FWHM
+        L, dLoL = 0, 0
+        data = empty_data1D(q, resolution=res, L=L, dL=L*dLoL)
         index = slice(None, None)
     return data, index
@@ -871 +874 @@
     # Plot if requested
     view = opts['view']
+    #view = 'log'
     if limits is None:
         vmin, vmax = np.inf, -np.inf

sasmodels/data.py

@@ -36 +36 @@
 
 import numpy as np  # type: ignore
+from numpy import sqrt, sin, cos, pi
 
 # pylint: disable=unused-import
@@ -301 +302 @@
 
 
-def empty_data1D(q, resolution=0.0):
+def empty_data1D(q, resolution=0.0, L=0., dL=0.):
     # type: (np.ndarray, float) -> Data1D
-    """
+    r"""
     Create empty 1D data using the given *q* as the x value.
 
-    *resolution* dq/q defaults to 5%.
+    rms *resolution* $\Delta q/q$ defaults to 0%.  If wavelength *L* and rms
+    wavelength divergence *dL* are defined, then *resolution* defines
+    rms $\Delta \theta/\theta$ for the lowest *q*, with $\theta$ derived from
+    $q = 4\pi/\lambda \sin(\theta)$.
     """
 
@@ -313 +317 @@
     Iq, dIq = None, None
     q = np.asarray(q)
-    data = Data1D(q, Iq, dx=resolution * q, dy=dIq)
+    if L != 0 and resolution != 0:
+        theta = np.arcsin(q*L/(4*pi))
+        dtheta = theta[0]*resolution
+        ## Solving Gaussian error propagation from
+        ##   Dq^2 = (dq/dL)^2 DL^2 + (dq/dtheta)^2 Dtheta^2
+        ## gives
+        ##   (Dq/q)^2 = (DL/L)**2 + (Dtheta/tan(theta))**2
+        ## Take the square root and multiply by q, giving
+        ##   Dq = (4*pi/L) * sqrt((sin(theta)*dL/L)**2 + (cos(theta)*dtheta)**2)
+        dq = (4*pi/L) * sqrt((sin(theta)*dL/L)**2 + (cos(theta)*dtheta)**2)
+    else:
+        dq = resolution * q
+
+    data = Data1D(q, Iq, dx=dq, dy=dIq)
     data.filename = "fake data"
     return data