Implement the following Matlab function (Algorithm 22.4 in Forsyth and Ponce):

function risk = CV_cross_validation(samples,num_to_omit)
%
%CV_cross_validation - Estimate risk by building several models and averaging cost
%On input:
%     samples (mxn array): sample data
%     num_to_omit (int): leave out this many to build classifier, then use omitted data to test
%On output:
%     risk (float): risk estimate
%Call:
%     r1 =  CV_cross_validation(samples1,2);
%Author:
%     Your name
%     UU
%     Fall 2012
%