diff options
| -rw-r--r-- | Doc/library/random.rst | 4 | ||||
| -rw-r--r-- | Lib/random.py | 24 | ||||
| -rw-r--r-- | Lib/test/test_random.py | 2 | ||||
| -rw-r--r-- | Misc/NEWS | 2 |
4 files changed, 31 insertions, 1 deletions
diff --git a/Doc/library/random.rst b/Doc/library/random.rst index 3beed6c..505cc81 100644 --- a/Doc/library/random.rst +++ b/Doc/library/random.rst @@ -190,6 +190,10 @@ be found in any statistics text. Return a random floating point number *N* such that ``a <= N < b``. +.. function:: triangular(low, high, mode) + + Return a random floating point number *N* such that ``low <= N < high`` + and with the specified *mode* between those bounds. .. function:: betavariate(alpha, beta) diff --git a/Lib/random.py b/Lib/random.py index ec0f386..13125e2 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -13,6 +13,7 @@ distributions on the real line: ------------------------------ uniform + triangular normal (Gaussian) lognormal negative exponential @@ -47,7 +48,7 @@ from binascii import hexlify as _hexlify __all__ = ["Random","seed","random","uniform","randint","choice","sample", "randrange","shuffle","normalvariate","lognormvariate", - "expovariate","vonmisesvariate","gammavariate", + "expovariate","vonmisesvariate","gammavariate","triangular", "gauss","betavariate","paretovariate","weibullvariate", "getstate","setstate","jumpahead", "WichmannHill", "getrandbits", "SystemRandom"] @@ -350,6 +351,25 @@ class Random(_random.Random): """Get a random number in the range [a, b).""" return a + (b-a) * self.random() +## -------------------- triangular -------------------- + + def triangular(self, low, high, mode): + """Triangular distribution. + + Continuous distribution bounded by given lower and upper limits, + and having a given mode value in-between. + + http://en.wikipedia.org/wiki/Triangular_distribution + + """ + u = self.random() + c = (mode - low) / (high - low) + if u > c: + u = 1 - u + c = 1 - c + low, high = high, low + return low + (high - low) * (u * c) ** 0.5 + ## -------------------- normal distribution -------------------- def normalvariate(self, mu, sigma): @@ -839,6 +859,7 @@ def _test(N=2000): _test_generator(N, gammavariate, (200.0, 1.0)) _test_generator(N, gauss, (0.0, 1.0)) _test_generator(N, betavariate, (3.0, 3.0)) + _test_generator(N, triangular, (0.0, 1.0, 1.0/3.0)) # Create one instance, seeded from current time, and export its methods # as module-level functions. The functions share state across all uses @@ -850,6 +871,7 @@ _inst = Random() seed = _inst.seed random = _inst.random uniform = _inst.uniform +triangular = _inst.triangular randint = _inst.randint choice = _inst.choice randrange = _inst.randrange diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py index 86e2e64..07e12d3 100644 --- a/Lib/test/test_random.py +++ b/Lib/test/test_random.py @@ -488,6 +488,7 @@ class TestDistributions(unittest.TestCase): g.random = x[:].pop; g.gammavariate(1.0, 1.0) g.random = x[:].pop; g.gammavariate(200.0, 1.0) g.random = x[:].pop; g.betavariate(3.0, 3.0) + g.random = x[:].pop; g.triangular(0.0, 1.0, 1.0/3.0) def test_avg_std(self): # Use integration to test distribution average and standard deviation. @@ -497,6 +498,7 @@ class TestDistributions(unittest.TestCase): x = [i/float(N) for i in xrange(1,N)] for variate, args, mu, sigmasqrd in [ (g.uniform, (1.0,10.0), (10.0+1.0)/2, (10.0-1.0)**2/12), + (g.triangular, (0.0, 1.0, 1.0/3.0), 4.0/9.0, 7.0/9.0/18.0), (g.expovariate, (1.5,), 1/1.5, 1/1.5**2), (g.paretovariate, (5.0,), 5.0/(5.0-1), 5.0/((5.0-1)**2*(5.0-2))), @@ -66,6 +66,8 @@ Library - Issue #2432: give DictReader the dialect and line_num attributes advertised in the docs. +- Issue #1681432: Add triangular distribution to the random module + - Issue #2136: urllib2's auth handler now allows single-quoted realms in the WWW-Authenticate header. |