CosmoCoffee

I have generated two data files of [tex]r[/tex] vs [tex]n_s[/tex] with different efoldings for natural inflation. I would like to plot them using python matplotlib and get the region between them filled with some color (as in the Planck paper 1502.02114 Fig.~ 12). I tried with fill_between function of matplotlib but couldn't get it as the x and y coordinates of the two data files have different size. Looking forward for kind help.

Regards,
akhilesh