From f248c4829e707e3b7379370c024c903123210404 Mon Sep 17 00:00:00 2001
From: Michael Clerx <michael.clerx@cs.ox.ac.uk>
Date: Wed, 31 Oct 2018 19:00:43 +0000
Subject: [PATCH] Fix to noise generation for older numpy versions

---
 pints/noise.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/pints/noise.py b/pints/noise.py
index cbef0f0c4..fc0a8487e 100644
--- a/pints/noise.py
+++ b/pints/noise.py
@@ -75,7 +75,11 @@ def ar1(rho, sigma, n):
         return np.array([])
 
     # Generate noise
-    v = np.random.normal(0, sigma * np.sqrt(1 - rho**2), n)
+    s = sigma * np.sqrt(1 - rho**2)
+    if s == 0:
+        v = np.zeros(n)
+    else:
+        v = np.random.normal(0, s, n)
     v[0] = np.random.rand()
     for t in range(1, n):
         v[t] += rho * v[t - 1]