RGBDSLAM v2 install error: No available formula for libg2o

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Hi, I installed ROS hydro on osx 10.9 already. Now I want to install RGBDSLAM v2 according to "Installation from scratch" http://felixendres.github.io/rgbdslam... .

But when $ rosdep install rgbdslam, I got the error

Error: No available formula for libg2o 
Please tap it and then try again: brew tap ros/hydro
executing command [brew install ros/hydro/libg2o]
Error: No available formula for libg2o 
Please tap it and then try again: brew tap ros/hydro
Searching formulae...
Searching taps...
ERROR: the following rosdeps failed to install
  homebrew: command [brew install ros/hydro/libg2o] failed

Then I installed g2o https://github.com/RainerKuemmerle/g2o . I still got the same error. I revised find_package(catkin REQUIRED COMPONENTS libg2o ...) as find_package(G2O REQUIRED) in the cmakelist, and the error is same.