Add docs

Author: timholy

README.md

@@ -178,11 +178,19 @@ julia> from_points = [[0, 0], [1, 0], [0, 1]];
 julia> to_points   = [[1, 1], [3, 1], [1.5, 3]];
 
 julia> AffineMap(from_points => to_points)
-AffineMap([1.9999999999999996 0.4999999999999999; -5.551115123125783e-16 2.0], [0.9999999999999999, 1.0000000000000002])
+AffineMap([2.0 0.5; 0.0 2.0], [1.0, 1.0])
 ```
 
 The points can be supplied as a collection of vectors or as a matrix with points as columns.
 
+If you want to restrict the transformation to be rigid (rotation + translation)
+or similar (rotation, translation, and scaling), use `kabsch` instead:
+
+```julia
+julia> rigid = kabsch(from_points => to_points)
+AffineMap([0.9912279006826346 0.132163720091018; -0.1321637200910178 0.9912279006826348], [1.4588694597421157, 1.380311939802794])
+```
+
 #### Perspective transformations
 
 The perspective transformation maps real-space coordinates to those on a virtual

docs/src/api.md

@@ -22,6 +22,7 @@ AffineMap(::Transformation, ::Any)
 AffineMap(::Pair)
 LinearMap
 Translation
+kabsch
 ```
 
 ## 2D Coordinates

docs/src/index.md

@@ -179,7 +179,7 @@ and a translation, e.g. `Translation(v) ∘ LinearMap(v)` (or any combination of
 
 `AffineMap`s can be constructed to fit point pairs `from_points => to_points`:
 
-```jldoctest; filter=[r"(2\.0|1\.9999\d+)" => "2.0", r"(0\.5|0\.49999\d+)" => "0.5", r"(0\.0|[ -]\d\.\d+e-\d\d)" => "0.0", r"(1\.0(?!0)|1\.0000\d+|0\.9999\d+)" => "1.0"]
+```jldoctest lsq; filter=[r"(2\.0|1\.9999\d+)" => "2.0", r"(0\.5|0\.49999\d+)" => "0.5", r"(0\.0|[ -]\d\.\d+e-\d\d)" => "0.0", r"(1\.0(?!0)|1\.0000\d+|0\.9999\d+)" => "1.0"]
 julia> from_points = [[0, 0], [1, 0], [0, 1]];
 
 julia> to_points   = [[1, 1], [3, 1], [1.5, 3]];
@@ -190,6 +190,15 @@ AffineMap([2.0 0.5; 0.0 2.0], [1.0, 1.0])
 
 (You may get slightly different numerical values due to roundoff errors.) The points can be supplied as a collection of vectors or as a matrix with points as columns.
 
+If you want to restrict the transformation to be rigid (rotation + translation)
+or similar (rotation, translation, and scaling), use `kabsch` instead:
+
+```jldoctest lsq; filter=[r"0\.9912\d+" => "0.9912", r"0\.1321\d+" => "0.1321", r"1\.4588\d+" => "1.4588", r"1\.3803" => "1.3803"]
+julia> rigid = kabsch(from_points => to_points)
+AffineMap([0.9912279006826346 0.132163720091018; -0.1321637200910178 0.9912279006826348], [1.4588694597421157, 1.380311939802794])
+```
+
+
 ### Perspective transformations
 
 The perspective transformation maps real-space coordinates to those on a virtual