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  • doc/guide/fitting_sq.rst

    r694c6d0 r3448301  
    1818of the form factor. For the theory behind this, see :ref:`PStheory` later. 
    1919 
    20 **If writing your own** $P@S$ **models, DO NOT give your model parameters** 
    21 **these names!** 
    22  
    2320Parameters 
    2421^^^^^^^^^^ 
     22 
     23**Except for volfraction, when writing your own** $P@S$ **models, DO NOT give** 
     24**your model parameters these names!** 
    2525 
    2626Many parameters are common amongst $P@S$ models, but take on specific meanings: 
    … …  
    3737    Structure factor models $S(Q)$ contain **volfraction**. In $P@S$ models 
    3838    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    $S(Q)$. 
    4142 
    4243    If the volume fraction required for $S(Q)$ is *not* the volume fraction 
    … …  
    7172    length. 
    7273 
    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 the parameter cannot then be 
     77    polydisperse). But **radius_effective** may also be specified directly, 
     78    independent of the estimate from $P(Q)$. 
    7879 
    7980    If **radius_effective** is calculated by $P(Q)$, it will be the 
    … …  
    8687.. note:: 
    8788 
    88    The following additional parameters are only available in SasView 5.0 and 
     89   The following additional parameters are only available in SasView 4.3 and 
    8990   later. 
    9091 
    … …  
    9495    be computed from the parameters of the shape. 
    9596 
    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 drop-down box. 
     97    When **radius_effective_mode = 0** then the unconstrained 
     98    **radius_effective** parameter in the $S(Q)$ model is used. *This is the* 
     99    *default in SasView versions 4.x and earlier*. Otherwise, in SasView 4.3 
     100    and later, **radius_effective_mode = k** represents an index in a list of 
     101    alternative **radius_effective** calculations. 
     102 
     103    In SasView 4.3 and later **k** must be entered as an integer (and it will 
     104    be necessary to read the source code file to discover what calculations the 
     105    modes represent), but in SasView 5.0 and later the options appear in a 
     106    drop-down box. 
    101107 
    102108    For example, the *ellipsoid* model defines the following 
    … …  
    144150    oscillations in the normal (local monodisperse) $S(Q)$. When $\beta(Q) = 1$ 
    145151    the local monodisperse approximation is recovered. *This mode is only* 
    146     *available in SasView 5.0 and later*. 
     152    *available in SasView 4.3 and later*. 
    147153 
    148154    More mode options may appear in future as more complicated operations are 
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