Changeset 339baa8 in sasmodels
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 Apr 1, 2019 5:59:53 AM (4 months ago)
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 master
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doc/guide/fitting_sq.rst
r694c6d0 r339baa8 18 18 of the form factor. For the theory behind this, see :ref:`PStheory` later. 19 19 20 **If writing your own** $P@S$ **models, DO NOT give your model parameters**21 **these names!**22 23 20 Parameters 24 21 ^^^^^^^^^^ 22 23 **Except for volfraction, when writing your own** $P@S$ **models, DO NOT give** 24 **your model parameters these names!** 25 25 26 26 Many parameters are common amongst $P@S$ models, but take on specific meanings: … … 37 37 Structure factor models $S(Q)$ contain **volfraction**. In $P@S$ models 38 38 this is *also* used as the volume fraction for the form factor model 39 $P(Q)$, *replacing* any **volfraction** parameter in $P(Q)$. This means 40 that $P@S$ models can also leave **scale** at 1.0. 39 $P(Q)$, so these models can also leave **scale** at 1.0. If $P(Q)$ already 40 has a **volfraction** parameter, it is tied to the **volfraction** for 41 $S(Q)$. 41 42 42 43 If the volume fraction required for $S(Q)$ is *not* the volume fraction … … 71 72 length. 72 73 73 In use, it may be sensible to tie or constrain **radius_effective** 74 to one or other of the "size" parameters describing the form of the shape. 75 76 **radius_effective** may also be specified directly, independent of the 77 estimate from $P(Q)$. 74 If **radius_effective_mode = 0** (see below) it may be sensible to tie or 75 constrain **radius_effective** to one or other of the "size" parameters 76 describing the form of the shape, although **radius_effective** may also 77 be specified directly, independent of the estimate from $P(Q)$. 78 78 79 79 If **radius_effective** is calculated by $P(Q)$, it will be the … … 86 86 .. note:: 87 87 88 The following additional parameters are only available in SasView 5.0and88 The following additional parameters are only available in SasView 4.3 and 89 89 later. 90 90 … … 94 94 be computed from the parameters of the shape. 95 95 96 When **radius_effective_mode = 0** then unconstrained **radius_effective** 97 parameter in the $S(Q)$ model is used. *This is the default in SasView* 98 *versions 4.x and earlier*. Otherwise, in SasView 5.0 and later, 99 **radius_effective_mode = k** represents an index in a list of alternative 100 **radius_effective** calculations which will appear in a dropdown box. 96 When **radius_effective_mode = 0** then the unconstrained 97 **radius_effective** parameter in the $S(Q)$ model is used. *This is the* 98 *default in SasView versions 4.x and earlier*. Otherwise, in SasView 4.3 99 and later, **radius_effective_mode = k** represents an index in a list of 100 alternative **radius_effective** calculations. 101 102 In SasView 4.3 and later **k** must be entered as an integer (and it will 103 be necessary to read the source code file to discover what calculations the 104 modes represent), but in SasView 5.0 and later the options appear in a 105 dropdown box. 101 106 102 107 For example, the *ellipsoid* model defines the following … … 144 149 oscillations in the normal (local monodisperse) $S(Q)$. When $\beta(Q) = 1$ 145 150 the local monodisperse approximation is recovered. *This mode is only* 146 *available in SasView 5.0and later*.151 *available in SasView 4.3 and later*. 147 152 148 153 More mode options may appear in future as more complicated operations are
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