From 1b9fb899513224a8ab8c5b2cdce2ea643f0e08f1 Mon Sep 17 00:00:00 2001
From: "tom.mok" <tom.mok@nib.co.nz>
Date: Mon, 20 Dec 2021 12:59:21 +1300
Subject: [PATCH 1/2] two by two det calculation

---
 .gitignore |  4 ++++
 det.py     | 12 ++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/.gitignore b/.gitignore
index 4d223ef..ff32beb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,7 @@
 .devcontainer/
 __pycache__/
 .pytest_cache/
+
+Scripts
+Lib
+pyvenv.cfg
diff --git a/det.py b/det.py
index 2f56473..9171149 100644
--- a/det.py
+++ b/det.py
@@ -12,4 +12,16 @@ def det(m: np.ndarray) -> float:
     :return: Determinant of the matrix
     """
 
+    if m.shape == (2, 2):
+        return (m[0][0] * m[1][1]) - (m[0][1] * m[1][0])
+
+    # iterate across top column
+    # for each element in top column multiply by inner matrix determinant
+    determinant  = 0
+
+    # for index, element in enumerate(m[0]):
+    #     innerMatrix = m[0:, 0:index index:-1]
+    #     determinant += element * det(innerMatrix)
+
+
     raise NotImplementedError()

From a2d3510bfb3dd588a8fc151217d20b9d1749f5da Mon Sep 17 00:00:00 2001
From: "tom.mok" <tom.mok@nib.co.nz>
Date: Mon, 20 Dec 2021 14:19:31 +1300
Subject: [PATCH 2/2] Recursive nxn algorithm for det

---
 det.py | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/det.py b/det.py
index 9171149..f8281d4 100644
--- a/det.py
+++ b/det.py
@@ -19,9 +19,12 @@ def det(m: np.ndarray) -> float:
     # for each element in top column multiply by inner matrix determinant
     determinant  = 0
 
-    # for index, element in enumerate(m[0]):
-    #     innerMatrix = m[0:, 0:index index:-1]
-    #     determinant += element * det(innerMatrix)
+    for index, element in enumerate(m[0]):
+        innerMatrix = np.delete(m, index, 1)[1:, :]
+        if (index % 2) == 0:
+            determinant += element * det(innerMatrix)
+        else:
+            determinant -= element * det(innerMatrix)
 
 
-    raise NotImplementedError()
+    return determinant