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#! /usr/bin/env python
import math, numpy
import lhapdf
import matplotlib.pyplot as plt
q = math.sqrt(6400.0)
pdfsets = ["cteq6ll.LHpdf", "MSTW2008lo68cl.LHgrid", "MRST2001lo.LHgrid", "MRST2007lomod.LHgrid", "MRSTMCal.LHgrid"]
#pdfsets = ["cteq6ll.LHpdf", "MRST2001lo.LHgrid", "MRST2007lomod.LHgrid", "MRSTMCal.LHgrid"]
partons = { 0 : "gluon", 2 : "up" }
NPOINTS = 1000
xs = numpy.logspace(-4, -0.001, NPOINTS)
plt.figure(figsize=(13,7))
for n, parton in enumerate(sorted(partons.keys())):
plt.subplot(1, len(partons), n+1)
lhapdf.initPDFSetByName(pdfsets[0])
lhapdf.initPDF(0)
refxfxs = numpy.zeros([NPOINTS])
for i, x in enumerate(xs):
xfx = lhapdf.xfx(x, q, parton)
refxfxs[i] = xfx
lines = []
for pdfset in pdfsets:
lhapdf.initPDFSetByName(pdfset)
lhapdf.initPDF(0)
xfxs = numpy.zeros([NPOINTS])
for i, x in enumerate(xs):
xfx = lhapdf.xfx(x, q, parton)
xfxs[i] = xfx
xfxratios = xfxs/refxfxs
l = plt.plot(xs, xfxratios)
lines.append(l)
plt.xscale("log")
plt.yscale("log")
plt.ylim(0.5, 3)
plt.yticks([0.6, 0.8, 1, 2, 3], ["0.6", "0.8", "1.0", "2.0", "3.0"])
plt.legend(lines, pdfsets)
plt.title(partons[parton])
plt.xlabel("$x$")
if n == 0:
plt.ylabel("$f(x, Q^2) / f(x, Q^2)_\\mathrm{CTEQ6ll}$")
plt.show()
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