added ability to link two parameters

build-docs.sh

@@ -0,0 +1 @@
+sphinx-build -M html docs/source/ docs/build/

docs/source/index.rst

@@ -80,13 +80,13 @@ The plots will be:
 
 The ``f.fit_df`` dataframe will look something like:
 
-+-------+-------+----------+-------+--------+---------+-------+-----------+
-| index | name  | estimate | std   | low_95 | high_95 | ...   | prior_std |
-+=======+=======+==========+=======+========+=========+=======+===========+
-| ``m`` | ``m`` | 5.009    | 0.045 | 4.817  | 5.202   | ...   | ``NaN``   |  
-+-------+-------+----------+-------+--------+---------+-------+-----------+
-| ``b`` | ``b`` | 5.644    | 0.274 |  4.465 | 6.822   | ...   | ``NaN``   |
-+-------+-------+----------+-------+--------+---------+-------+-----------+
++-------+-------+----------+-------+--------+---------+-------+-----------+--------+
+| index | name  | estimate | std   | low_95 | high_95 | ...   | prior_std | parent |
++=======+=======+==========+=======+========+=========+=======+===========+========+
+| ``m`` | ``m`` | 5.009    | 0.045 | 4.817  | 5.202   | ...   | ``NaN``   | ``NA`` | 
++-------+-------+----------+-------+--------+---------+-------+-----------+--------+
+| ``b`` | ``b`` | 5.644    | 0.274 |  4.465 | 6.822   | ...   | ``NaN``   | ``NA`` |
++-------+-------+----------+-------+--------+---------+-------+-----------+--------+
 
 The ``f.fit_quality`` dataframe will look something like:
 
@@ -292,15 +292,15 @@ can control seven attributes of each fittable parameter. These are stored in
 
     f.param_df
 
-+-------+-------+-----------+-------------+-------------+------------+-----------+
-| name  | guess | fixed     | lower_bound | upper_bound | prior_mean | prior_std |
-+=======+=======+===========+=============+=============+============+===========+
-| ``a`` | 0.0   | ``False`` | ``-inf``    | ``inf``     | ``NaN``    | ``NaN``   |
-+-------+-------+-----------+-------------+-------------+------------+-----------+
-| ``b`` | 2.0   | ``False`` | ``-inf``    | ``inf``     | ``NaN``    | ``NaN``   |
-+-------+-------+-----------+-------------+-------------+------------+-----------+
-| ``c`` | 3.0   | ``False`` | ``-inf``    | ``inf``     | ``NaN``    | ``NaN``   |
-+-------+-------+-----------+-------------+-------------+------------+-----------+
++-------+-------+-----------+-------------+-------------+------------+-----------+--------+
+| name  | guess | fixed     | lower_bound | upper_bound | prior_mean | prior_std | parent |
++=======+=======+===========+=============+=============+============+===========+========+
+| ``a`` | 0.0   | ``False`` | ``-inf``    | ``inf``     | ``NaN``    | ``NaN``   | ``NA`` |
++-------+-------+-----------+-------------+-------------+------------+-----------+--------+
+| ``b`` | 2.0   | ``False`` | ``-inf``    | ``inf``     | ``NaN``    | ``NaN``   | ``NA`` |
++-------+-------+-----------+-------------+-------------+------------+-----------+--------+
+| ``c`` | 3.0   | ``False`` | ``-inf``    | ``inf``     | ``NaN``    | ``NaN``   | ``NA`` |
++-------+-------+-----------+-------------+-------------+------------+-----------+--------+
 
 The ``f.param_df`` dataframe can be accessed and edited using standard 
 `pandas DataFrame <pandas-dataframe_>`_ commands. The ``name`` column is set
@@ -363,6 +363,12 @@ The full rules for the parameter dataframe are:
 +-----------------+---------------------------------------------------------+
 | ``prior_std``   | single float value; ``np.nan`` allowed (see note)       |
 +-----------------+---------------------------------------------------------+
+| ``parent``      | string name of a parameter. If this is specified, it    |
+|                 | tells the fitter to forces the parameter and its parent |
+|                 | to have the same value during the analysis. This lowers |
+|                 | the number of floating parameters by one. To remove a   |
+|                 | link, set this value to ``pd.NA`` or ``None``.          |
++-----------------+---------------------------------------------------------+
 
 .. note:: 
 
@@ -378,7 +384,7 @@ The full rules for the parameter dataframe are:
     ``prior_mean`` and ``prior_std`` to ``np.nan``. 
 
 -----------------------------
-4. Set non-fittable arguments
+1. Set non-fittable arguments
 -----------------------------
 
 One can specify arguments to the function that should not be used as fit
@@ -594,13 +600,13 @@ Parameter values (fit_df)
 One accesses the parameter estimates via the ``f.fit_df`` pandas dataframe. The
 ``fit_df`` output from the `Simple example`_ above is:
 
-+-------+-------+----------+-------+--------+---------+-------+-----------+
-| index | name  | estimate | std   | low_95 | high_95 | ...   | prior_std |
-+=======+=======+==========+=======+========+=========+=======+===========+
-| ``m`` | ``m`` | 5.009    | 0.045 | 4.817  | 5.202   | ...   | ``NaN``   |  
-+-------+-------+----------+-------+--------+---------+-------+-----------+
-| ``b`` | ``b`` | 5.644    | 0.274 |  4.465 | 6.822   | ...   | ``NaN``   |
-+-------+-------+----------+-------+--------+---------+-------+-----------+
++-------+-------+----------+-------+--------+---------+-------+----------+
+| index | name  | estimate | std   | low_95 | high_95 | ...   | parent   |
++=======+=======+==========+=======+========+=========+=======+==========+
+| ``m`` | ``m`` | 5.009    | 0.045 | 4.817  | 5.202   | ...   | ``NA``   |  
++-------+-------+----------+-------+--------+---------+-------+----------+
+| ``b`` | ``b`` | 5.644    | 0.274 |  4.465 | 6.822   | ...   | ``NA``   |
++-------+-------+----------+-------+--------+---------+-------+----------+
 
 All three methods (ml, bootstrap, and mcmc) will have identical columns. These
 columns report similar, but not identical, features of each parameter for each