Thread: Strange data fitting problem View Single Post
P: 312
 Quote by Stephen Tashi Are you saying that vector 'a' will be chosen so that the vector Ua will be 1 at the jth component iff the largest singular value occurs in S at location S[j][j] and the vector Ua will be zero elsewhere? In these two examples, do we have the same matrix for A'D but different answers for the maximum angle? (My 4-D intuition isn't good, so I'm not sure.) Example 1: $A = \begin{pmatrix} \frac{1}{\sqrt{3}} \\ \frac{1}{\sqrt{3}}\\ \frac{2}{\sqrt{15}}\\ \frac{1}{\sqrt{15}} \end{pmatrix} ,\ D = \begin{pmatrix} 1 & 0 \\ 0 & 1 \\ 0 & 0 \\ 0 & 0 \end{pmatrix}$ Example 2: $A = \begin{pmatrix} \frac{1}{\sqrt{3}} \\ \frac{1}{\sqrt{3}}\\ \frac{1}{\sqrt{6}}\\ \frac{1}{\sqrt{6}} \end{pmatrix} ,\ D = \begin{pmatrix} 1 & 0 \\ 0 & 1 \\ 0 & 0 \\ 0 & 0 \end{pmatrix}$
As I solved this example, since A'*D is the same, so are a and b, actually a=1 and b=[1/sqrt(2),1/sqrt(2)]. But x1=A1≠x2=A2. However the angle is the same, since <x,y>=(Ua)'*S*(Vb) is totally determined by A'*D. Seemingly logical.