cleaning up

doc/src/week34/week34.do.txt

@@ -1205,7 +1205,7 @@ ways of dealing with outliers.
 The Huber cost function is defined as
 !bt
 \[
-H_{\delta}(a)=\left\{\begin{array}\frac{1}{2}a^{2}&{\text{for }}|a|\leq \delta ,\\ \delta (|a|-{\frac {1}{2}\delta ),&{\text{otherwise.}\end{array}\right.
+H_{\delta}(a)=\left\{\begin{array}\frac{1}{2}a^{2}&{\text{for }}|a|\leq \delta ,\\ \delta (|a|-\frac {1}{2}\delta ),&{\text{otherwise.}\end{array}\right.
 \]
 !et
 Here $a=\bm{y} - \bm{\tilde{y}}$.