Remove bundle diameter from tuto

Author: EmmaRenauld

docs/source/documentation/bundle_analysis/bundle_diameter_fitting_function.rst

@@ -7,7 +7,6 @@ This section covers bundle analysis methods in scilpy.
    :maxdepth: 1
 
    tractogram_segmentation
-   bundle_diameter_fitting_function
    profilometry
    tractometry
    create_population_template

docs/source/documentation/bundle_analysis/index.rst

@@ -17,6 +17,22 @@
     - or if fanning is in 2 directions (uniform dispersion), leads to a good
       approximation
 
+Fitting func
+------------
+Choices are:
+- None: Default, all points are weighted equally no matter their
+        (normalized 0-1) distance to the barycenter.
+- lin_up: Points are weighted using their distance to the barycenter
+        (linear, x). Farther = increased weight. Bigger envelope.
+- lin_down: Points are weighted using their distance to the barycenter
+        (linear, 1-x). Farther = decreased weight. Smaller envelope.
+- exp: Points are weighted using their distance to the barycenter
+        (exponential, e^x). Farther = decreased weight. Smaller envelope.
+- inv: Points are weighted using their distance to the barycenter
+        (inverse, 1/x). Farther = decreased weight. Much smaller envelope.
+- log: Points are weighted using their distance to the barycenter
+        (logarithmic, ln x+1). Farther = increased weight. Bigger envelope.
+
 The scripts prints a JSON file with mean/std. This is compatible with our
 tractometry scripts.
 WARNING: STD is in fact an ERROR measure from the fit and NOT an STD.