diff --git a/tests/probability/test_subtract_rvs.py b/tests/probability/test_subtract_rvs.py new file mode 100644 index 000000000..a020940e0 --- /dev/null +++ b/tests/probability/test_subtract_rvs.py @@ -0,0 +1,60 @@ +import numpy as np +import scipy.stats + +import sdr + + +def test_normal_normal(): + X = scipy.stats.norm(loc=-1, scale=0.5) + Y = scipy.stats.norm(loc=2, scale=1.5) + _verify(X, Y) + + +def test_rayleigh_rayleigh(): + X = scipy.stats.rayleigh(scale=1) + Y = scipy.stats.rayleigh(loc=1, scale=2) + _verify(X, Y) + + +def test_rician_rician(): + X = scipy.stats.rice(2) + Y = scipy.stats.rice(3) + _verify(X, Y) + + +def test_normal_rayleigh(): + X = scipy.stats.norm(loc=-1, scale=0.5) + Y = scipy.stats.rayleigh(loc=2, scale=1.5) + _verify(X, Y) + + +def test_rayleigh_rician(): + X = scipy.stats.rayleigh(scale=1) + Y = scipy.stats.rice(3) + _verify(X, Y) + + +def _verify(X, Y): + # Numerically compute the distribution + Z = sdr.subtract_rvs(X, Y) + + # Empirically compute the distribution + z = X.rvs(100_000) - Y.rvs(100_000) + hist, bins = np.histogram(z, bins=101, density=True) + x = bins[1:] - np.diff(bins) / 2 + + if False: + import matplotlib.pyplot as plt + + plt.figure() + plt.plot(x, X.pdf(x), label="X") + plt.plot(x, Y.pdf(x), label="Y") + plt.plot(x, Z.pdf(x), label="X - Y") + plt.hist(z, bins=101, cumulative=False, density=True, histtype="step", label="X - Y empirical") + plt.legend() + plt.xlabel("Random variable") + plt.ylabel("Probability density") + plt.title("Difference of two distributions") + plt.show() + + assert np.allclose(Z.pdf(x), hist, atol=np.max(hist) * 0.1)