Symbolic Fitting; fitting as it should be.

## Project description

Please cite this DOI if `symfit` benefited your publication. Building this has been a lot of work, and as young researchers your citation means a lot to us.
Martin Roelfs & Peter C Kroon, symfit. doi:10.5281/zenodo.1133336

## Documentation

## Project Goals

The goal of this project is simple: to make fitting in Python pythonic. What does pythonic fitting look like? Well, there’s a simple test. If I can give you pieces of example code and don’t have to use any additional words to explain what it does, it’s pythonic.

from symfit import parameters, variables, Fit, Model xdata = [1.0, 2.0, 3.0, 4.0, 5.0] ydata = [2.3, 3.3, 4.1, 5.5, 6.7] yerr = [0.1, 0.1, 0.1, 0.1, 0.1] a, b = parameters('a, b') x, y = variables('x, y') model = Model({y: a * x + b}) fit = Fit(model, x=xdata, y=ydata, sigma_y=yerr) fit_result = fit.execute()

Cool right? So now that we have done a fit, how do we use the results?

import matplotlib.pyplot as plt yfit = model(x=xdata, **fit_result.params)[y] plt.plot(xdata, yfit) plt.show()

Need I say more? How about I let another code example do the talking?

from symfit import parameters, Fit, Equality, GreaterThan x, y = parameters('x, y') model = 2 * x * y + 2 * x - x**2 - 2 * y**2 constraints = [ Equality(x**3, y), GreaterThan(y, 1), ] fit = Fit(- model, constraints=constraints) fit_result = fit.execute()

I know what you are thinking. “What if I need to fit to a system of Ordinary Differential Equations?”

from symfit import variables, Parameter, ODEModel, Fit, D tdata = np.array([10, 26, 44, 70, 120]) adata = 10e-4 * np.array([44, 34, 27, 20, 14]) a, b, t = variables('a, b, t') k = Parameter('k', 0.1) model_dict = { D(a, t): - k * a**2, D(b, t): k * a**2, } ode_model = ODEModel(model_dict, initial={t: 0.0, a: 54 * 10e-4, b: 0.0}) fit = Fit(ode_model, t=tdata, a=adata, b=None) fit_result = fit.execute()

For more fitting delight, check the docs at http://symfit.readthedocs.org.

## Project details

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