Added determinate function (#1429)

* Added determinate function

* Changed determinate function name

* Changed instance of .det() to .determinate()

* Added force_test() function

* Update tests.py

linear_algebra/src/lib.py

@@ -277,6 +277,33 @@ class Matrix(object):
         """
         return self.__height
 
+    def determinate(self) -> float:
+        """
+            returns the determinate of an nxn matrix using Laplace expansion
+        """
+        if self.__height == self.__width and self.__width >= 2:
+            total = 0
+            if self.__width > 2:
+                for x in range(0, self.__width):
+                    for y in range(0, self.__height):
+                        total += (
+                            self.__matrix[x][y]
+                            * (-1) ** (x + y)
+                            * Matrix(
+                                self.__matrix[0:x] + self.__matrix[x + 1 :],
+                                self.__width - 1,
+                                self.__height - 1,
+                            ).determinate()
+                        )
+            else:
+                return (
+                    self.__matrix[0][0] * self.__matrix[1][1]
+                    - self.__matrix[0][1] * self.__matrix[1][0]
+                )
+            return total
+        else:
+            raise Exception("matrix is not square")
+
     def __mul__(self, other):
         """
             implements the matrix-vector multiplication.