# Changeset 339baa8 in sasmodels

Ignore:
Timestamp:
Apr 1, 2019 5:59:53 AM (4 months ago)
Branches:
master
Children:
3448301
Parents:
d827c5e
Message:

Text update at PK request

File:
1 edited

### Legend:

Unmodified
 r694c6d0 of the form factor. For the theory behind this, see :ref:PStheory later. **If writing your own** $P@S$ **models, DO NOT give your model parameters** **these names!** Parameters ^^^^^^^^^^ **Except for volfraction, when writing your own** $P@S$ **models, DO NOT give** **your model parameters these names!** Many parameters are common amongst $P@S$ models, but take on specific meanings: Structure factor models $S(Q)$ contain **volfraction**. In $P@S$ models this is *also* used as the volume fraction for the form factor model $P(Q)$, *replacing* any **volfraction** parameter in $P(Q)$. This means that $P@S$ models can also leave **scale** at 1.0. $P(Q)$, so these models can also leave **scale** at 1.0.  If $P(Q)$ already has a **volfraction** parameter, it is tied to the **volfraction** for $S(Q)$. If the volume fraction required for $S(Q)$ is *not* the volume fraction length. In use, it may be sensible to tie or constrain **radius_effective** to one or other of the "size" parameters describing the form of the shape. **radius_effective** may also be specified directly, independent of the estimate from $P(Q)$. If **radius_effective_mode = 0** (see below) it may be sensible to tie or constrain **radius_effective** to one or other of the "size" parameters describing the form of the shape, although **radius_effective** may also be specified directly, independent of the estimate from $P(Q)$. If **radius_effective** is calculated by $P(Q)$, it will be the .. note:: The following additional parameters are only available in SasView 5.0 and The following additional parameters are only available in SasView 4.3 and later. be computed from the parameters of the shape. When **radius_effective_mode = 0** then unconstrained **radius_effective** parameter in the $S(Q)$ model is used. *This is the default in SasView* *versions 4.x and earlier*. Otherwise, in SasView 5.0 and later, **radius_effective_mode = k** represents an index in a list of alternative **radius_effective** calculations which will appear in a drop-down box. When **radius_effective_mode = 0** then the unconstrained **radius_effective** parameter in the $S(Q)$ model is used. *This is the* *default in SasView versions 4.x and earlier*. Otherwise, in SasView 4.3 and later, **radius_effective_mode = k** represents an index in a list of alternative **radius_effective** calculations. In SasView 4.3 and later **k** must be entered as an integer (and it will be necessary to read the source code file to discover what calculations the modes represent), but in SasView 5.0 and later the options appear in a drop-down box. For example, the *ellipsoid* model defines the following oscillations in the normal (local monodisperse) $S(Q)$. When $\beta(Q) = 1$ the local monodisperse approximation is recovered. *This mode is only* *available in SasView 5.0 and later*. *available in SasView 4.3 and later*. More mode options may appear in future as more complicated operations are