Interpolate with lmfit?
There is not a built-in way to automatically interpolate with lmfit.  With a lmfit Model, you provide the array on independent values at which the Model should be evaluated, and an array of data to compared to that model.
You're free to interpolate or smooth the data or perform some other transformation (I sometimes Fourier transform data and model to emphasize some frequencies), but you'll have to include that as part of the model.
I am trying to fit a curve with lmfit but the data set I'm working with does not contain a lot of points and this makes the resulting fit look jagged instead of curved.
I'm simply using the line:
out = mod.fit(SV, pars, x=VR)
were VR and SV are the coordinates of the points I'm trying to fit.
I've tried using scipy.interpolate.UnivariateSpline and the fitted the resulting data but I want to know if there is a built-in or faster way to do this. 
Thank you