From dd3188b798b94bad673886d0565f27b264abc1ae Mon Sep 17 00:00:00 2001
From: Josh Burman <jburman@yas.getyardstick.com>
Date: Fri, 29 Oct 2021 05:43:32 +0000
Subject: [PATCH] construct based irt library and add item response function

---
 app/lib/irt/item_information_function.py       |  0
 app/lib/irt/item_response_function.py          | 12 ++++++++++++
 app/lib/irt/models/three_parameter_logistic.py | 13 +++++++++++++
 app/lib/irt/test_information_function.py       |  0
 app/lib/irt/test_response_function.py          |  0
 5 files changed, 25 insertions(+)
 create mode 100644 app/lib/irt/item_information_function.py
 create mode 100644 app/lib/irt/item_response_function.py
 create mode 100644 app/lib/irt/models/three_parameter_logistic.py
 create mode 100644 app/lib/irt/test_information_function.py
 create mode 100644 app/lib/irt/test_response_function.py

diff --git a/app/lib/irt/item_information_function.py b/app/lib/irt/item_information_function.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/lib/irt/item_response_function.py b/app/lib/irt/item_response_function.py
new file mode 100644
index 0000000..a844f08
--- /dev/null
+++ b/app/lib/irt/item_response_function.py
@@ -0,0 +1,12 @@
+from models.three_parameter_logitistc import ThreeParameterLogistic
+
+class ItemResponseFunction():
+  def __init__(self, irt_model):
+    self.model_data = irt_model
+
+  def calculate(self, **kwargs):
+    if self.model_data.model == '3PL':
+      return ThreeParameterLogistic.new(self.model_data, kwargs).result
+    else:
+      # potentially error out
+      return None
diff --git a/app/lib/irt/models/three_parameter_logistic.py b/app/lib/irt/models/three_parameter_logistic.py
new file mode 100644
index 0000000..a5e2986
--- /dev/null
+++ b/app/lib/irt/models/three_parameter_logistic.py
@@ -0,0 +1,13 @@
+class ThreeParameterLogistic:
+  def __init__(self, model_params, kwargs):
+    self.model_params = model_params
+    # check if exists, if not error out
+    self.b_param = kwargs['b_param']
+    self.e = 2.71828
+    self.theta = kwargs['theta']
+
+  def result(self):
+    a = self.model_params.a
+    c = self.model_params.c
+
+    return c + (1 - c) * (1 / (1 + e**(-a * (self.theta - self.b_param))))
diff --git a/app/lib/irt/test_information_function.py b/app/lib/irt/test_information_function.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/lib/irt/test_response_function.py b/app/lib/irt/test_response_function.py
new file mode 100644
index 0000000..e69de29