Merge pull request #3368 from dynikon/fix-docs

Fix typos in HalfNormal and Wald

Author: lucianopaz

pymc3/distributions/continuous.py

@@ -697,8 +697,8 @@ class HalfNormal(PositiveContinuous):
            \sqrt{\frac{2\tau}{\pi}}
            \exp\left(\frac{-x^2 \tau}{2}\right)
 
-       f(x \mid \sigma) =\sigma
-           \sqrt{\frac{2}{\pi}}
+       f(x \mid \sigma) =
+           \sqrt{\frac{2}{\pi\sigma^2}}
            \exp\left(\frac{-x^2}{2\sigma^2}\right)
 
     .. note::
@@ -833,7 +833,7 @@ class Wald(PositiveContinuous):
     .. math::
 
        f(x \mid \mu, \lambda) =
-           \left(\frac{\lambda}{2\pi)}\right)^{1/2} x^{-3/2}
+           \left(\frac{\lambda}{2\pi}\right)^{1/2} x^{-3/2}
            \exp\left\{
                -\frac{\lambda}{2x}\left(\frac{x-\mu}{\mu}\right)^2
            \right\}