What is the Moore-Penrose pseudoinverse A+A^+A+ of a diagonal matrix D=diag(d1,d2,…,dn)D = \text{diag}(d_1, d_2, \dots, d_n)D=diag(d1,d2,…,dn) where some di=0d_i = 0di=0?
diag(d1−1,…,dn−1)\text{diag}(d_1^{-1}, \dots, d_n^{-1})diag(d1−1,…,dn−1)
diag(d1+,…,dn+)\text{diag}(d_1^+, \dots, d_n^+)diag(d1+,…,dn+) where di+=1/did_i^+ = 1/d_idi+=1/di if di≠0d_i \neq 0di=0 and 000 otherwise
The pseudoinverse does not exist.
diag(0,…,0)\text{diag}(0, \dots, 0)diag(0,…,0)