matlab 命令pdist, pdist2

D = pdist2(X,Y,Distance) %default=Euclidean distance

e.g:

X = rand(3,2)
Y = [X(1:2,:); rand(1,2)];
XX1 = pdist2(X,Z)  %3*3
Z=rand(1,2);
XX2 = pdist2(X,Z)  %3*1小结：结果中如XX2(3,2)位置的值，来源于X(3,:)与Y(2,:)的距离计算，等价于pdist2(X(3,:),Y(2,:))

D = pdist(X) %default=Euclidean distance

e.g:

X = rand(3,2);
D = pdist(X) %1*3
%值顺序如下
pdist2(X(1,:),X(2,:)) , pdist2(X(1,:),X(3,:)), pdist2(X(2,:),X(3,:))