c++ - How to use OpenCV train_hog.cpp -

i'm trying use opencv train_hog utility.

when try compile with

g++ -ggdb `pkg-config --cflags --libs opencv` train_hog.cpp -o train_hog 

i ton of different errors.

train_hog.cpp:11:21: error: ‘ml’ not namespace-name  using namespace cv::ml;                      ^ train_hog.cpp:11:23: error: expected namespace-name before ‘;’ token  using namespace cv::ml; 

and few pages more.

can give me instructions how use or point me working solution?