Legend

see: https://stackoverflow.com/a/43439132

import numpy as np
from smpl import plot
from smpl import io
from smpl import functions as f
import uncertainties.unumpy as unp

data = np.loadtxt(io.find_file('test_linear_data.txt',3))
xdata = data[:,0]
xerr = data[:,2]
ydata = data[:,1]
yerr = data[:,3]
x = unp.uarray(xdata,xerr)
y = unp.uarray(ydata,yerr)

data

array([[0. , 1. , 0.1, 0.2],
       [1. , 2. , 0.2, 0.1],
       [2. , 3. , 0.3, 0.1],
       [3. , 5. , 0.1, 0.4],
       [4. , 5. , 0.1, 0.1],
       [5. , 6. , 0.1, 0.2]])

ff = plot.fit(xdata, ydata, fmt='.', label='data', lpos=6,bbox_to_anchor=(1.04,0.5),xaxis="x in a.u.",yaxis="y in a.u.",function=f.linear, params=[1])

ff = plot.fit(xdata, ydata, fmt='.', lpos=2,bbox_to_anchor=(0,1.02,1,0.2),ncol=3,label='data', xaxis="x in a.u.",yaxis="y in a.u.",function=f.line, params=[1,2])