CAMB Output

Complete workflow: configure CAMB, compute, wrap with CambOutput, plot all observables.

Optional dependency

This example requires the camb Python package:

pip install cplots[camb]

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

---

Setup

import camb
import numpy as np
import cplots

pars = camb.set_params(
    H0=67.4, ombh2=0.022, omch2=0.12,
    mnu=0.06, omk=0, tau=0.054,
    As=2.1e-9, ns=0.965,
    lmax=2500,
    redshifts=[0.0, 0.5, 1.0],
    WantTransfer=True,
)
results = camb.get_results(pars)

out = cplots.CambOutput(results)

---

Background evolution

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

Plot only H(z) and luminosity distance:

bg = out.background(
    quantities=["H [km/s/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()

Because pk() uses an interpolator internally, z does not need to appear in the pre-computed redshift list passed to set_params:

fig = cplots.Figure()
for z in [0.0, 0.3, 0.7, 1.5]:
    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

Computed analytically from the inflation parameters (As, ns, pivot_scalar) — no extra CAMB output flag needed:

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

---

Thermodynamics

Not available for CAMB

thermodynamics() raises NotImplementedError for CambOutput. CAMB does not expose a visibility table equivalent to CLASS's thermodynamics output. Use ClassOutput if you need thermodynamic background quantities.