plot minimum spanning tree

I calculated MST according to the euclidian distance between each point. I used this code to colored the MST edges according to weight but it doesn't work !!

%% Compute minimal spanning tree [G,pred] = graphminspantree(G,'Method','Kruskal');

%% nn = 20; cmap = jet(nn); p1 = min(pred); p2 = max(pred); [h,idx] = histc(pred,p1:(p2-p1)/(nn-1):p2); x = V(:,1); % graph vertices y = V(:,2); figure; for i=1:length(pred) plot(x(i),y(i),'-','color',cmap(idx(i),:)); >>> the proplem here hold on; end end