CLASS Output

Complete workflow: configure CLASS, compute, wrap with ClassOutput, plot all observables.

Optional dependency

This example requires the classy Python package:

pip install cplots[classy]

The code blocks below show the actual calls verbatim but are not executed during the docs build because classy is an optional dependency.

---

Setup

from classy import Class
import cplots

cosmo = Class()
cosmo.set({
    "h": 0.6736,
    "Omega_b": 0.02237,
    "Omega_cdm": 0.1200,
    "A_s": 2.100e-9,
    "n_s": 0.9649,
    "tau_reio": 0.0544,
    "output": "tCl pCl lCl mPk",
    "lensing": "yes",
    "P_k_max_h/Mpc": 1.0,
    "z_max_pk": 2.0,
    "l_max_scalars": 2500,
})
cosmo.compute()

out = cplots.ClassOutput(cosmo)

---

Background evolution

bg = out.background()
cplots.BackgroundEvolution(bg).show()

Plot only H(z) and luminosity distance:

bg = out.background(
    quantities=["H [1/Mpc]", "lum. dist."],
    labels={"lum. dist.": r"$d_L$ [Mpc]"},
)
cplots.BackgroundEvolution(bg).show()

---

Matter power spectrum

Linear P(k) at z=0 in h/Mpc units:

pk = out.pk(z=0.0, k_min=1e-4, k_max=1.0, n_k=300)
cplots.PKSpectrum(pk).show()

Multiple redshifts on the same axes:

import cplots

fig = cplots.Figure()
for z in [0.0, 0.5, 1.0, 2.0]:
    pk = out.pk(z=z, n_k=300)
    fig.add(cplots.PKSpectrum(pk, label=f"z={z}"))
fig.show()

---

CMB angular power spectra

TT, EE, and TE spectra with the standard ℓ(ℓ+1)/2π scaling:

cls = out.cl(spectra=["tt", "ee", "te"], lensed=True, ell_factor=True)
cplots.ClSpectrum(cls).show()

Unlensed TT only, in K²:

cls = out.cl(spectra=["tt"], lensed=False, units="K2")
cplots.ClSpectrum(cls).show()

---

Primordial power spectrum

prim = out.primordial()
cplots.PKSpectrum(prim).show()

---

Thermodynamics

Visibility function against redshift:

thermo = out.thermodynamics()
cplots.BackgroundEvolution(thermo).show()

Multiple thermodynamic quantities:

thermo = out.thermodynamics(quantities=["g [Mpc^-1]", "Tb [K]"])
cplots.BackgroundEvolution(thermo).show()

---

Cleanup

Always free CLASS memory when done:

cosmo.struct_cleanup()
cosmo.empty()