..

hugo/content/py/fitting/_index.md

@@ -18,4 +18,8 @@ BornAgain supports
 In the following we will show how to fit using the BornAgain Python API.
 For fitting through the graphical user interface, see [GUI > Fitting](/gui/gui-fitting).
 
+For most examples,
+the environment variable `BA_DATA_DIR` must point
+to the copy of directory {{% ref-src "testdata" %}} in your local BornAgain installation.
+
 {{% children depth="2" %}}

rawEx/fit/algo/fit_rosenbrock.py

@@ -2,7 +2,6 @@
 
 import bornagain as ba
 
-
 def rosenbrock(params):
     x = params["x"].value
     y = params["y"].value
@@ -10,7 +9,6 @@ def rosenbrock(params):
     tmp2 = 1 - x
     return 100*tmp1*tmp1 + tmp2*tmp2
 
-
 params = ba.Parameters()
 params.add("x", value=-1.2, min=-5.0, max=5.0, step=0.01)
 params.add("y", value=1.0, min=-5.0, max=5.0, step=0.01)