%matplotlib inline
from lmfit import Model, Fitter
import numpy as np

data = np.array([1,2,3,4,5,4,3,2])
x = np.arange(len(data))

fitter = Fitter(data, x=x)

fitter

fitter.current_result.values

other_data = np.array([10, 11, 12, 11, 10, 8, 7, 6])
fitter.data = other_data

def func(x, a=1):
    "a very simple model indeed"
    return x + a

class UserDefinedModel(Model):
    def __init__(self, *args, **kwargs):
        super(UserDefinedModel, self).__init__(func, *args, **kwargs)

data = np.array([1,2,3,4,5,4,3,2])
x = np.arange(len(data))

fitter = Fitter(data, x=x)

fitter