Add missing snippet for sign/cwiseSign functions.
diff --git a/doc/snippets/Cwise_sign.cpp b/doc/snippets/Cwise_sign.cpp
new file mode 100644
index 0000000..49920e4
--- /dev/null
+++ b/doc/snippets/Cwise_sign.cpp
@@ -0,0 +1,2 @@
+Array3d v(-3,5,0);
+cout << v.sign() << endl;
diff --git a/doc/snippets/MatrixBase_cwiseSign.cpp b/doc/snippets/MatrixBase_cwiseSign.cpp
new file mode 100644
index 0000000..efd7179
--- /dev/null
+++ b/doc/snippets/MatrixBase_cwiseSign.cpp
@@ -0,0 +1,4 @@
+MatrixXd m(2,3);
+m << 2, -4, 6,
+ -5, 1, 0;
+cout << m.cwiseSign() << endl;