--- a/allan.py	Fri Apr 18 18:44:54 2014 +0200
+++ b/allan.py	Tue Mar 24 18:10:10 2015 +0100
@@ -4,7 +4,7 @@
 import numexpr
 
 __all__ = ['outliers', 'detrend', 'fastdetrend', 
-           'adev', 'xadev', 'xmdev', 'xtdev', 'xavar', 'xmvar', ]
+           'adev', 'xadev', 'xmdev', 'xtdev', 'xavar', 'xmvar', 'tau' ]
 
 
 def outliers(y, alpha=6, remove=False):
@@ -50,6 +50,14 @@
     return y
 
 
+def tau(expmin=0, expmax=4):
+    return np.ravel(np.power(10, np.arange(expmin, expmax))[:,np.newaxis] * np.arange(0, 10))
+
+
+def tau124(expmin=0, expmax=4):
+    return np.ravel(np.power(10.0, np.arange(expmin, expmax))[:,np.newaxis] * np.array([1, 2, 4]))
+
+
 def adev(x, tau, sampl=1.0):
     """Allan deviation"""