About a error of your example :Should get exactly one excerpt for input parameters in the string

[kirito521]

I run your example and get that:
ValueError: Should get exactly one excerpt for input parameters in the string.
May I get some help for that? Thanks！

[kirito521]

-- coding: utf-8 --

Copyright (c) 2020, Matgenix SRL, All rights reserved.

Distributed open source for academic and non-profit users.

Contact Matgenix for commercial usage.

See LICENSE file for details.

"""Example usage of pysisso for a regression using sklearn interface."""

import matplotlib.pyplot as plt
import numpy as np

from pysisso.sklearn import SISSORegressor

Define general parameters

TITLE = "f(x) = 0.5x^3 + 0.5x^2 - 4.0*x - 4.0"
NPOINTS = 100 # Number of data points
SIGMA = 0.5 # Randomness in the data points
PLOT_FIGURES = True # whether to interactively plot the figures with matplotlib
SAVE_FIGURES = False # whether to save the matplotlib figures to a file
CLEAN_RUN_DIR = True # whether to remove the SISSO_dir after the fit

Set the random seed to always keep the same figure

np.random.seed(42)

Define the function:

f(x) = 0.5x^3 + 0.5x^2 - 4.0*x - 4.0 (roots = [-2.0, -1.0, 2.0])

def fun(xx, const=1.0):
return 0.5 * xx ** 3 + 0.5 * xx ** 2 - 4.0 * 0.5 * xx - 4.0 * const

Define the data set

X = np.random.uniform(-2.5, 2.5, NPOINTS)
y = fun(X) + np.random.normal(0.0, scale=SIGMA, size=NPOINTS)

Plot true function and data

xlin = np.linspace(-3, 3, 1000)
ylin = fun(xlin)
fig, subplot = plt.subplots()
subplot.plot(xlin, ylin, "-", color="C0", label="True function")
subplot.plot(X, y, "o", color="C1", label="Data")
subplot.set_xlabel("x")
subplot.set_ylabel("f(x)")
subplot.set_title(TITLE)
subplot.legend()
if SAVE_FIGURES:
fig.savefig("true_data.pdf")
if PLOT_FIGURES:
plt.show()

Define the regressor, fit the data and predict

sisso_regressor = SISSORegressor(
rung=1,
opset="(+)(*)(^2)(^3)(^-1)(cos)(sin)",
desc_dim=3,
clean_run_dir=CLEAN_RUN_DIR,
)
X = X.reshape(-1, 1) # only one feature, X is initially defined as 1D, sklearn needs 2D
sisso_regressor.fit(X, y)
ylin_pred = sisso_regressor.predict(xlin)

Plot the true and predicted functions, together with the data

fig, subplot = plt.subplots()
subplot.plot(xlin, ylin, "-", color="C0", label="True function")
subplot.plot(X, y, "o", color="C1", label="Data")
subplot.plot(xlin, ylin_pred, "-", color="C2", label="Predicted function")
subplot.set_xlabel("x")
subplot.set_ylabel("f(x)")
subplot.set_title(TITLE)
subplot.legend()
if SAVE_FIGURES:
fig.savefig("true_data_pred.pdf")
if PLOT_FIGURES:
plt.show()

[chr218]

I run your example and get that: ValueError: Should get exactly one excerpt for input parameters in the string. May I get some help for that? Thanks！

Inside the "Previous_Versions" directory, extract "SISSO.3.0.2" to your /home directory and follow the installation per the "README". I found that the output format is different for each version; and pysisso only works with V3.0.2. Also, you may run into a "forrtl: severe (174): SIGSEGV, segmentation fault" error. Try executing "ulimit -s unlimited" before rerunning cubic_function.py.