Add doctest example to FundamentalMatrixTransform class (#6863)

* Add example to fundamental matrix class
* Fix precision for parameters
* Fix precision of estimate function
* Fix precision of inverse function
* Add description to examples

Co-authored-by: Lars Grüter <lagru+github@mailbox.org>

skimage/transform/_geometric.py

@@ -252,6 +252,58 @@ class FundamentalMatrixTransform(_GeometricTransform):
     params : (3, 3) array
         Fundamental matrix.
 
+    Examples
+    --------
+    >>> import numpy as np
+    >>> import skimage as ski
+    >>> tform_matrix = ski.transform.FundamentalMatrixTransform()
+
+    Define source and destination points:
+
+    >>> src = np.array([1.839035, 1.924743,
+    ...                 0.543582, 0.375221,
+    ...                 0.473240, 0.142522,
+    ...                 0.964910, 0.598376,
+    ...                 0.102388, 0.140092,
+    ...                15.994343, 9.622164,
+    ...                 0.285901, 0.430055,
+    ...                 0.091150, 0.254594]).reshape(-1, 2)
+    >>> dst = np.array([1.002114, 1.129644,
+    ...                 1.521742, 1.846002,
+    ...                 1.084332, 0.275134,
+    ...                 0.293328, 0.588992,
+    ...                 0.839509, 0.087290,
+    ...                 1.779735, 1.116857,
+    ...                 0.878616, 0.602447,
+    ...                 0.642616, 1.028681]).reshape(-1, 2)
+
+    Estimate the transformation matrix:
+
+    >>> tform_matrix.estimate(src, dst)
+    True
+    >>> tform_matrix.params
+    array([[-0.2178588368,  0.4192819131, -0.0343074756],
+           [-0.0717941428,  0.0451643229,  0.0216072614],
+           [ 0.2480621133, -0.4294781423,  0.0221019139]])
+
+    Compute the Sampson distance:
+
+    >>> tform_matrix.residuals(src, dst)
+    array([0.0053886022, 0.0052610069, 0.086897007 , 0.0185053395,
+           0.0941825909, 0.0018596663, 0.0616048944, 0.0265513581])
+
+    Apply inverse transformation:
+
+    >>> tform_matrix.inverse(dst)
+    array([[-0.0513590998,  0.0417097392,  0.0121304255],
+           [-0.2159949601,  0.2919341852,  0.0097818351],
+           [-0.0079222047,  0.0375888939, -0.0091538874],
+           [ 0.1418718406, -0.2798895924,  0.0247650748],
+           [ 0.0589007483, -0.073544809 , -0.0048134227],
+           [-0.2198526747,  0.3671746435, -0.01482408  ],
+           [ 0.0133956875, -0.0338812341,  0.0049760468],
+           [ 0.0342092683, -0.1135811955,  0.0222823604]])
+
     """
 
     def __init__(self, matrix=None, *, dimensionality=2):