Sigmoid custom operator

[YoannBonnet]

Hello,

I want to add a new unary operator when defining my PySRRegressor, which is the sigmoid function. I define it as follows:

model_2 = PySRRegressor(
    niterations=50,
    binary_operators=[‘+’, ‘-’, ‘*’, ‘/’],
    unary_operators=[‘exp’, ‘inv(x) = 1/x’, ‘sig(x)=1/(1+exp(-x))’],
    extra_sympy_mappings = {
        ‘inv": lambda x: 1/x,
        ‘sig": lambda x: 1/(1+np.exp(-x))
    },
    **default_pysr_params,
)

I get the following error:

ValueError                                Traceback (most recent call last)
ValueError: Error from parse_expr with transformed code: <code object <module> at 0x7f62306e5f20, file "<string>", line 1>

The above exception was the direct cause of the following exception:

TypeError                                 Traceback (most recent call last)
File /home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/export_sympy.py:91, in pysr2sympy(equation, feature_names_in, extra_sympy_mappings)
     [90](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/export_sympy.py:90) try:
---> [91](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/export_sympy.py:91)     return sympify(equation, locals=local_sympy_mappings, evaluate=False)
     [92](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/export_sympy.py:92) except TypeError as e:

File /home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/core/sympify.py:493, in sympify(a, locals, convert_xor, strict, rational, evaluate)
    [492](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/core/sympify.py:492)     a = a.replace('\n', '')
--> [493](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/core/sympify.py:493)     expr = parse_expr(a, local_dict=locals, transformations=transformations, evaluate=evaluate)
    [494](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/core/sympify.py:494) except (TokenError, SyntaxError) as exc:

File /home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:1090, in parse_expr(s, local_dict, transformations, global_dict, evaluate)
   [1089](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:1089)     local_dict[i] = null
-> [1090](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:1090) raise e from ValueError(f"Error from parse_expr with transformed code: {code!r}")

File /home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:1081, in parse_expr(s, local_dict, transformations, global_dict, evaluate)
   [1080](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:1080) try:
-> [1081](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:1081)     rv = eval_expr(code, local_dict, global_dict)
   [1082](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:1082)     # restore neutral definitions for names

File /home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:909, in eval_expr(code, local_dict, global_dict)
    [904](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:904) """
    [905](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:905) Evaluate Python code generated by ``stringify_expr``.
    [906](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:906) 
    [907](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:907) Generally, ``parse_expr`` should be used.
    [908](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:908) """
--> [909](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:909) expr = eval(
    [910](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:910)     code, global_dict, local_dict)  # take local objects in preference
    [911](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/sympy/parsing/sympy_parser.py:911) return expr

File <string>:1

Cell In[10], [line 7](vscode-notebook-cell:?execution_count=10&line=7)
      [1](vscode-notebook-cell:?execution_count=10&line=1) model_2 = PySRRegressor(
      [2](vscode-notebook-cell:?execution_count=10&line=2)     niterations=50,
      [3](vscode-notebook-cell:?execution_count=10&line=3)     binary_operators=["+", "-", "*", "/"],
      [4](vscode-notebook-cell:?execution_count=10&line=4)     unary_operators=["exp", "inv(x) = 1/x", "sig(x)=1/(1+exp(-x))"],
      [5](vscode-notebook-cell:?execution_count=10&line=5)     extra_sympy_mappings = {
      [6](vscode-notebook-cell:?execution_count=10&line=6)         "inv": lambda x: 1/x,
----> [7](vscode-notebook-cell:?execution_count=10&line=7)         "sig": lambda x: 1/(1+np.exp(-x))
      [8](vscode-notebook-cell:?execution_count=10&line=8)     },
      [9](vscode-notebook-cell:?execution_count=10&line=9)     **default_pysr_params,
     [10](vscode-notebook-cell:?execution_count=10&line=10) )

TypeError: loop of ufunc does not support argument 0 of type Mul which has no callable exp method

The above exception was the direct cause of the following exception:

TypeError                                 Traceback (most recent call last)
Cell In[11], [line 1](vscode-notebook-cell:?execution_count=11&line=1)
----> [1](vscode-notebook-cell:?execution_count=11&line=1) model_2.fit(X, y)

File /home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2087, in PySRRegressor.fit(self, X, y, Xresampled, weights, variable_names, complexity_of_variables, X_units, y_units)
   [2084](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2084)     self._checkpoint()
   [2086](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2086) # Perform the search:
-> [2087](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2087) self._run(X, y, runtime_params, weights=weights, seed=seed)
   [2089](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2089) # Then, after fit, we save again, so the pickle file contains
   [2090](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2090) # the equations:
   [2091](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2091) if not self.temp_equation_file:

File /home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:1921, in PySRRegressor._run(self, X, y, runtime_params, weights, seed)
   [1918](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:1918) self.julia_state_stream_ = jl_serialize(out)
   [1920](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:1920) # Set attributes
-> [1921](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:1921) self.equations_ = self.get_hof()
   [1923](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:1923) if self.delete_tempfiles:
   [1924](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:1924)     shutil.rmtree(self.tempdir_)

File /home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2412, in PySRRegressor.get_hof(self)
   [2409](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2409) torch_format = []
   [2411](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2411) for _, eqn_row in output.iterrows():
-> [2412](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2412)     eqn = pysr2sympy(
   [2413](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2413)         eqn_row["equation"],
   [2414](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2414)         feature_names_in=self.feature_names_in_,
   [2415](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2415)         extra_sympy_mappings=self.extra_sympy_mappings,
   [2416](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2416)     )
   [2417](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2417)     sympy_format.append(eqn)
   [2419](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/sr.py:2419)     # NumPy:

File /home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/export_sympy.py:95, in pysr2sympy(equation, feature_names_in, extra_sympy_mappings)
     [93](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/export_sympy.py:93) if "got an unexpected keyword argument 'evaluate'" in str(e):
     [94](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/export_sympy.py:94)     return sympify(equation, locals=local_sympy_mappings)
---> [95](https://vscode-remote+wsl-002bwsl4datascience.vscode-resource.vscode-cdn.net/home/default/miniconda/envs/bibsr-pysr/lib/python3.10/site-packages/pysr/export_sympy.py:95) raise TypeError(f"Error processing equation '{equation}'") from e

TypeError: Error processing equation '(x0 * sig(x0)) * 2.1461575'

Do you have any ideas on how to resolve this error?

Thank you in advance.

[MilesCranmer]

It's because np.exp is not a sympy function. You need to use sympy.exp