bugfix for v0.8.4

MatthewReid854 · May 5, 2022 · 8264678 · 8264678
1 parent 5c481b0
commit 8264678
Show file tree

Hide file tree

Showing 4 changed files with 31 additions and 2 deletions.
diff --git a/docs/Changelog.rst b/docs/Changelog.rst
@@ -5,6 +5,17 @@
 Changelog
 ---------
 
+**Version: 0.8.4 --- Released: 05 May 2022**
+''''''''''''''''''''''''''''''''''''''''''''
+
+**Summary of changes**
+
+This is bugfix release to deal with a minor bug.
+
+**Bug Fixes**
+
+-    Weibull Mixture models and Weibull Competing Risks models obtain their initial guesses by splitting the data into two groups and fitting a Weibull distribution to each group. If there are not two distinct groups, the estimate for the dividing line between the two groups may result in one of the groups having fewer than 2 failures allocated to the group. This causes an error when fitting the Weibull distribution to that group. It has been fixed by checking the number of elements in the group and moving the dividing line if required. The dividing line is only an estimate used to obtain the initial guess for the parameters and the dividing line is not used in the final MLE or LS estimates in the fitter.
+
 **Version: 0.8.3 --- Released: 17 Apr 2022**
 ''''''''''''''''''''''''''''''''''''''''''''
 

diff --git a/reliability/Fitters.py b/reliability/Fitters.py
@@ -3679,6 +3679,15 @@ def __init__(
         else:
             dividing_line = right_div_line
 
+        number_of_items_in_group_1 = len(np.where(failures<dividing_line)[0])
+        number_of_items_in_group_2 = len(failures) - number_of_items_in_group_1
+        if number_of_items_in_group_1 < 2:
+            failures_sorted = np.sort(failures)
+            dividing_line = (failures_sorted[1]+failures_sorted[2])/2 # adjusts the dividing line in case there aren't enough failures in the first group
+        if number_of_items_in_group_2 < 2:
+            failures_sorted = np.sort(failures)
+            dividing_line = (failures_sorted[-2]+failures_sorted[-3])/2 # adjusts the dividing line in case there aren't enough failures in the second group
+
         # this is the point at which data is assigned to one group or another for the purpose of generating the initial guess
         GROUP_1_failures = []
         GROUP_2_failures = []
@@ -4164,6 +4173,15 @@ def __init__(
         else:
             dividing_line = right_div_line
 
+        number_of_items_in_group_1 = len(np.where(failures<dividing_line)[0])
+        number_of_items_in_group_2 = len(failures) - number_of_items_in_group_1
+        if number_of_items_in_group_1 < 2:
+            failures_sorted = np.sort(failures)
+            dividing_line = (failures_sorted[1]+failures_sorted[2])/2 # adjusts the dividing line in case there aren't enough failures in the first group
+        if number_of_items_in_group_2 < 2:
+            failures_sorted = np.sort(failures)
+            dividing_line = (failures_sorted[-2]+failures_sorted[-3])/2 # adjusts the dividing line in case there aren't enough failures in the second group
+
         # this is the point at which data is assigned to one group or another for the purpose of generating the initial guess
         GROUP_1_failures = []
         GROUP_2_failures = []

diff --git a/reliability/__init__.py b/reliability/__init__.py
@@ -16,7 +16,7 @@
 from datetime import date
 
 __title__ = 'reliability'
-__version__ = "0.8.3"
+__version__ = "0.8.4"
 __description__ = 'A Python library for reliability engineering'
 __url__ = 'https://reliability.readthedocs.io/en/latest/index.html'
 __author__ = 'Matthew Reid'

diff --git a/setup.py b/setup.py
@@ -7,7 +7,7 @@
 
 setuptools.setup(
     name="reliability",
-    version="0.8.3",
+    version="0.8.4",
     description="Reliability Engineering toolkit for Python",
     author="Matthew Reid",
     author_email="alpha.reliability@gmail.com",