matlab矩阵元素位置怎么返回?

FIND Find indices of nonzero elements。
I = FIND(X) returns the indices of the vector X that are
non-zero。For example,I = FIND(A>100),returns the indices
of A where A is greater than 100。See RELOP。
[I,J] = FIND(X) returns the row and column indices of
the nonzero entries in the matrix X。This is often used
with sparse matrices。
[I,J,V] = FIND(X) also returns a vector containing the
nonzero entries in X。Note that find(X) and find(X~=0)
will produce the same I and J,but the latter will produce
a V with all 1's。
See also SPARSE,IND2SUB。