Why 'Linkage' returns wrong result??

I use the distance matrix as W =

     0     1     0     5
     1     0     0     1
     0     0     0     3
     5     1     3     0

>> Z=linkage(W,'single')

Z =

    2.0000    3.0000    2.2361
    1.0000    5.0000    2.2361
    4.0000    6.0000    5.1962

>> Z=linkage(W,'complete')

Z =

    2.0000    3.0000    2.2361
    1.0000    5.0000    4.2426
    4.0000    6.0000    7.6811

above are wrong results

Somebody could tell me why,please??

Answer 1

[Tom Lane]

Your distance matrix isn't in the vector form that pdist computes and linkage expects. So linkage is treating it as a data matrix. Try this:

    Z=linkage(squareform(W),'single')

[YF]

O,it works,thank you for your help