how to calculate resultant motion vector

By using blockmatcher of matlab i been able to sketch out motion vectors for current frame by comparing it with reference frame. I want to found resultant motion vector for current frame but can't find any way to perform this is task. Your kind guidance is required. I am attaching my code as well and

clear all; clc; workspace;

img1 = im2double(rgb2gray(imread('D:\Mattiiiilab\bin\5269.jpg'))); img2= im2double(rgb2gray(imread('D:\Mattiiiilab\bin\5291.jpg')));

hbm = vision.BlockMatcher('ReferenceFrameSource',... 'Input port','BlockSize',[101 101]); hbm.OutputValue = 'Horizontal and vertical components in complex form'; hbm.SearchMethod= 'Three-step'; motion = step(hbm,img1,img2);

[X Y] = meshgrid(1:101:size(img1,2),1:101:size(img1,1)); imshow(img2); hold on; quiver(X(:),Y(:),real(motion(:)),imag(motion(:)),0); hold off;

I have attached an image showing motion vectors as well