trueydata = vcurve(truexdata, 1.0)
xdata = truexdata + 0.1 * numpy.random.randn(8)
ydata = trueydata + 0.1 * numpy.random.randn(8)
popt, pcov = scipy.optimize.curve_fit(vcurve, xdata, ydata, p0=[2.0])
print(popt)
Fitting data with integral function