resolution calculation does not check for basis of support between q points (Trac #715)

[pkienzle]

To compute the resolution approximation more accurately all measured q points should have enough calculated q points within the resolution window regardless of how sparsely the data is measured.

sasmodels/resolution.py only extends q beyond the measured end points, it does not check that there is sufficient number of points within dq of each measured q point. This is generally not a problem for SANS since the 1D pattern is computed from the circular average with dense enough spacing, but it could potentially be a problem when datasets from non-overlapping q regions are joined, or when data is excluded from the middle of the q range. It could also be a problem in USANS where q spacing is completely under user control.

Migrated from http://trac.sasview.org/ticket/715

{
    "status": "new",
    "changetime": "2017-10-27T16:44:10",
    "_ts": "2017-10-27 16:44:10.398319+00:00",
    "description": "To compute the resolution approximation more accurately all measured q points should have enough calculated q points within the resolution window regardless of how sparsely the data is measured.\n\nsasmodels/resolution.py only extends q beyond the measured end points, it does not check that there is sufficient number of points within dq of each measured q point.  This is generally not a problem for SANS since the 1D pattern is computed from the circular average with dense enough spacing, but it could potentially be a problem when datasets from non-overlapping q regions are joined, or when data is excluded from the middle of the q range.  It could also be a problem in USANS where q spacing is completely under user control.",
    "reporter": "pkienzle",
    "cc": "",
    "resolution": "",
    "workpackage": "SasView Bug Fixing",
    "time": "2016-10-06T16:15:37",
    "component": "SasView",
    "summary": "resolution calculation does not check for basis of support between q points",
    "priority": "minor",
    "keywords": "",
    "milestone": "SasView 4.3.0",
    "owner": "",
    "type": "defect"
}

[pkienzle]

Trac update at 2017/08/09 20:44:40:

• pkienzle commented:

Yet another user wanted to fit a model with an excluded region in the middle. The GUI does not support masking central parts of the q range, and the resolution calculator does not fill the masked range with q calculation points, leading to poorly fitting points at the edges of the masked region.

• pkienzle changed milestone from "SasView Next Release +1" to "SasView 4.2.0"

[butlerpd]

Trac update at 2017/10/27 16:44:10: butler changed milestone from "SasView 4.2.0" to "SasView 4.3.0"