function [avg] = AveragePrecision(Outputs,test_target)
%Computing the average precision
%Outputs: the predicted outputs of the classifier, the output of the ith instance for the jth class is stored in Outputs(j,i)
%test_target: the actual labels of the test instances, if the ith instance belong to the jth class, test_target(j,i)=1, otherwise test_target(j,i)=-1

    [num_class,~]=size(Outputs);
    index = (sum(test_target)~=num_class)&(sum(test_target)~=-num_class);
    temp_Outputs = Outputs(:,index);
    temp_test_target = test_target(:,index);
    [~,num_instance]=size(temp_Outputs);

    avg = 0;
    for i = 1:num_instance
        temp_avg = 0;
        rel_l = find(temp_test_target(:,i)>0);
        for j = rel_l'
            temp_avg = temp_avg + mean(temp_test_target(temp_Outputs(:,i)>=temp_Outputs(j,i),i)==1);
        end
        avg = avg + temp_avg / length(rel_l);
    end
    avg = avg / num_instance;
end