Fix :meth:~.input_to_graph_point when passing a line_graph (#1994)

* Fix the bounds of the binary search

* Fix the binary_search when the point in on a bound (return the proportion instead of the function value)

* Add an error when x is not in the graph range

* Allow to pass a VMobject to input_to_graph_point (type of a line_graph?)

* Modify the test to reflect fixed bug

* Update according to pre-commit

* Add the exception in the docstring

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Convert a string into f-string

Co-authored-by: Léo Géré <leo.gere@inrae.fr>
Co-authored-by: Laith Bahodi <70682032+hydrobeam@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Léo Géré <gere@etud.insa-toulouse.fr>

Author: 5 people

manim/mobject/coordinate_systems.py

@@ -33,7 +33,13 @@
 )
 from ..mobject.number_line import NumberLine
 from ..mobject.svg.tex_mobject import MathTex
-from ..mobject.types.vectorized_mobject import Mobject, VDict, VectorizedPoint, VGroup
+from ..mobject.types.vectorized_mobject import (
+    Mobject,
+    VDict,
+    VectorizedPoint,
+    VGroup,
+    VMobject,
+)
 from ..utils.color import (
     BLACK,
     BLUE,
@@ -699,7 +705,11 @@ def get_parametric_curve(self, function, **kwargs):
         graph.underlying_function = function
         return graph
 
-    def input_to_graph_point(self, x: float, graph: "ParametricFunction") -> np.ndarray:
+    def input_to_graph_point(
+        self,
+        x: float,
+        graph: Union["ParametricFunction", VMobject],
+    ) -> np.ndarray:
         """Returns the coordinates of the point on a ``graph`` corresponding to an ``x`` value.
 
         Examples
@@ -730,6 +740,11 @@ def construct(self):
         -------
         :class:`np.ndarray`
             The coordinates of the point on the :attr:`graph` corresponding to the :attr:`x` value.
+
+        Raises
+        ------
+        :exc:`ValueError`
+            When the target x is not in the range of the line graph.
         """
 
         if hasattr(graph, "underlying_function"):
@@ -740,13 +755,15 @@ def construct(self):
                     0
                 ],
                 target=x,
-                lower_bound=self.x_range[0],
-                upper_bound=self.x_range[1],
+                lower_bound=0,
+                upper_bound=1,
             )
             if alpha is not None:
                 return graph.point_from_proportion(alpha)
             else:
-                return None
+                raise ValueError(
+                    f"x={x} not located in the range of the graph ([{self.p2c(graph.get_start())[0]}, {self.p2c(graph.get_end())[0]}])",
+                )
 
     def i2gp(self, x: float, graph: "ParametricFunction") -> np.ndarray:
         """

manim/utils/simple_functions.py

@@ -95,9 +95,9 @@ def binary_search(function, target, lower_bound, upper_bound, tolerance=1e-4):
         mh = np.mean([lh, rh])
         lx, mx, rx = (function(h) for h in (lh, mh, rh))
         if lx == target:
-            return lx
+            return lh
         if rx == target:
-            return rx
+            return rh
 
         if lx <= target and rx >= target:
             if mx > target:

tests/test_coordinate_system.py

@@ -107,7 +107,14 @@ def test_coords_to_point():
 def test_input_to_graph_point():
     ax = Axes()
     curve = ax.get_graph(lambda x: np.cos(x))
+    line_graph = ax.get_line_graph([1, 3, 5], [-1, 2, -2], add_vertex_dots=False)[
+        "line_graph"
+    ]
 
     # move a square to PI on the cosine curve.
     position = np.around(ax.input_to_graph_point(x=PI, graph=curve), decimals=4)
     assert np.array_equal(position, (2.6928, -0.75, 0))
+
+    # test the line_graph implementation
+    position = np.around(ax.input_to_graph_point(x=PI, graph=line_graph), decimals=4)
+    assert np.array_equal(position, (2.6928, 1.2876, 0))