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| author | kai-striega <kaistriega@gmail.com> | 2019-09-14 13:45:00 +0800 |
|---|---|---|
| committer | kai-striega <kaistriega@gmail.com> | 2019-09-14 17:14:03 +0800 |
| commit | 594d0c39bd7baf9575411b4a9689ec0bd564c930 (patch) | |
| tree | add9598f3e66013157b46f8194be34341b5bcebf /numpy/lib | |
| parent | 58dc45505b3d3e2b9de1a6961a749c8bd1165548 (diff) | |
| download | numpy-594d0c39bd7baf9575411b4a9689ec0bd564c930.tar.gz | |
TST: Move NPV-IRR congruence check to tests
The internal rate of return (irr) is defined as the rate of return
required for the net present values of a series of cashflows to be
zero. i.e the lowest rate of return required for a project to break
even.
This is currently checked by refering to the example output from
the ``irr`` and ``npv`` function documentation. This commit adds a
test to confirm the identity holds.
Diffstat (limited to 'numpy/lib')
| -rw-r--r-- | numpy/lib/financial.py | 7 | ||||
| -rw-r--r-- | numpy/lib/tests/test_financial.py | 6 |
2 files changed, 6 insertions, 7 deletions
diff --git a/numpy/lib/financial.py b/numpy/lib/financial.py index d135804c0..d72384e99 100644 --- a/numpy/lib/financial.py +++ b/numpy/lib/financial.py @@ -715,8 +715,6 @@ def irr(values): >>> round(np.irr([-5, 10.5, 1, -8, 1]), 5) 0.0886 - (Compare with the Example given for numpy.lib.financial.npv) - """ # `np.roots` call is why this function does not support Decimal type. # @@ -785,11 +783,6 @@ def npv(rate, values): Examples -------- - >>> np.npv(0.281,[-100, 39, 59, 55, 20]) - -0.0084785916384548798 # may vary - - (Compare with the Example given for numpy.lib.financial.irr) - Consider a potential project with an initial investment of $40 000 and projected cashflows of $5 000, $8 000, $12 000 and $30 000 at the end of each period discounted at a rate of 8% per period. To find the project's diff --git a/numpy/lib/tests/test_financial.py b/numpy/lib/tests/test_financial.py index 524915041..21088765f 100644 --- a/numpy/lib/tests/test_financial.py +++ b/numpy/lib/tests/test_financial.py @@ -9,6 +9,12 @@ from numpy.testing import ( class TestFinancial(object): + def test_npv_irr_congruence(self): + # IRR is defined as the rate required for the present value of a + # a series of cashflows to be zero i.e. NPV(IRR(x), x) = 0 + cashflows = np.array([-40000, 5000, 8000, 12000, 30000]) + assert_allclose(np.npv(np.irr(cashflows), cashflows), 0, atol=1e-10, rtol=0) + def test_rate(self): assert_almost_equal( np.rate(10, 0, -3500, 10000), |