Make whitened residuals available

CHANGELOG-unreleased.md

@@ -42,6 +42,7 @@ the released changes.
 - `ScaleToaError.register_toasigma_deriv_funcs` method to populate derivatives of scaled TOA uncertainties.
 - `ScaleToaError.d_toasigma_d_EFAC` and `ScaleToaError.d_toasigma_d_EQUAD` methods.
 - Separate `.fullname` for all observatories
+- `Residuals.calc_whitened_resids()` method
 ### Fixed
 - Wave model `validate()` can correctly use PEPOCH to assign WAVEEPOCH parameter
 - Fixed RTD by specifying theme explicitly.

src/pint/residuals.py

@@ -500,6 +500,12 @@ def calc_time_resids(
             )
         return (phase_resids / self.get_PSR_freq(calctype=calctype)).to(u.s)
 
+    def calc_whitened_resids(self):
+        r = self.calc_time_resids()
+        nr = sum(self.noise_resids.values())
+        sigma = self.get_data_error()
+        return ((r - nr) / sigma).to(u.dimensionless_unscaled)
+
     def _calc_gls_chi2(self, lognorm=False):
         """Compute the chi2 when correlated noise is present in the timing model.
         If the system is not singular, it uses Cholesky factorization to evaluate this.

tests/test_residuals.py

@@ -12,7 +12,7 @@
 from numpy.testing import assert_allclose
 from pinttestdata import datadir
 
-from pint.fitter import GLSFitter, WidebandTOAFitter, WLSFitter
+from pint.fitter import Fitter, GLSFitter, WidebandTOAFitter, WLSFitter
 from pint.models import get_model
 from pint.residuals import CombinedResiduals, Residuals, WidebandTOAResiduals
 import pint.residuals
@@ -438,3 +438,46 @@ def test_resid_mean_phase():
     mean, _ = pint.residuals.weighted_mean(full, w)
     assert mean == r.calc_phase_mean()
     assert r.calc_phase_mean() == r2.calc_phase_mean()
+
+
+@pytest.mark.parametrize(
+    "par",
+    [
+        """
+        PSRJ J1234+5678
+        ELAT 0
+        ELONG 0
+        DM 10
+        F0 1
+        PEPOCH 58000
+        EFAC mjd 57000 58000 2
+        """,
+        """
+        PSRJ J1234+5678
+        ELAT 0
+        ELONG 0
+        DM 10
+        F0 1
+        PEPOCH 58000
+        TNRedAmp -14.227505410948254
+        TNRedGam 4.91353
+        TNRedC 45
+        """,
+    ],
+)
+def test_whitened_res(par):
+    m = get_model(StringIO(par))
+    t = make_fake_toas_uniform(
+        57000,
+        59000,
+        20,
+        model=m,
+        error=1 * u.us,
+        add_noise=True,
+        add_correlated_noise=m.has_correlated_errors,
+    )
+
+    ftr = Fitter.auto(t, m)
+    ftr.fit_toas()
+
+    assert np.isclose(ftr.resids.calc_whitened_resids().std(), 1, atol=0.75)