diff --git a/examples/kcentroid_ex.cpp b/examples/kcentroid_ex.cpp
index 967065557..a0b91b7a2 100644
--- a/examples/kcentroid_ex.cpp
+++ b/examples/kcentroid_ex.cpp
@@ -33,6 +33,8 @@ double sinc(double x)
 int main()
 {
     // Here we declare that our samples will be 2 dimensional column vectors.  
+    // (Note that if you don't know the dimensionality of your vectors at compile time
+    // you can change the 2 to a 0 and then set the size at runtime)
     typedef matrix<double,2,1> sample_type;
 
     // Now we are making a typedef for the kind of kernel we want to use.  I picked the
diff --git a/examples/kkmeans_ex.cpp b/examples/kkmeans_ex.cpp
index e20e5b304..fd6112d4c 100644
--- a/examples/kkmeans_ex.cpp
+++ b/examples/kkmeans_ex.cpp
@@ -30,6 +30,8 @@ using namespace dlib;
 int main()
 {
     // Here we declare that our samples will be 2 dimensional column vectors.  
+    // (Note that if you don't know the dimensionality of your vectors at compile time
+    // you can change the 2 to a 0 and then set the size at runtime)
     typedef matrix<double,2,1> sample_type;
 
     // Now we are making a typedef for the kind of kernel we want to use.  I picked the
diff --git a/examples/krls_ex.cpp b/examples/krls_ex.cpp
index a935fa68d..331faca7b 100644
--- a/examples/krls_ex.cpp
+++ b/examples/krls_ex.cpp
@@ -29,6 +29,8 @@ int main()
     // Here we declare that our samples will be 1 dimensional column vectors.  The reason for
     // using a matrix here is that in general you can use N dimensional vectors as inputs to the
     // krls object.  But here we only have 1 dimension to make the example simple.
+    // (Note that if you don't know the dimensionality of your vectors at compile time
+    // you can change the first number to a 0 and then set the size at runtime)
     typedef matrix<double,1,1> sample_type;
 
     // Now we are making a typedef for the kind of kernel we want to use.  I picked the