OpenCV C++ implementation for estimating and scoring homography in image mosaic computation

I want to calculate mosaic of two images in OpenCV C++ as calculated in sift_mosaic() function implemented in vlfeat library available at the link http://ift.tt/1AlJwkk. I am having difficulty to convert code in "RANSAC with homography model" section as I couldn't find equivalent functions in C++ for cat(), vl_hat(), vl_colsubset() etc.. functions of matlab.

Can someone please provide me OpenCV C++ code for estimating homography and scoring homography.