MATLAB中求矩阵非零元的坐标：

方法1：

index=find(a);[i,j]=ind2sub(size(a),index);disp([i,j])

 

方法2：

[i,j]=find(a>0|a<0) %列出所有非零元的坐标 [i,j]=find(a==k) %找出等于k值的矩阵元素的坐标

 

所用函数简介：

IND2SUB Multiple subscripts from linear index.

IND2SUB is used to determine the equivalent subscript values

corresponding to a given single index into an array.

[I,J] = IND2SUB(SIZ,IND) returns the arrays I and J containing the

equivalent row and column subscripts corresponding to the index

matrix IND for a matrix of size SIZ.

For matrices, [I,J] = IND2SUB(SIZE(A),FIND(A>5)) returns the same

values as [I,J] = FIND(A>5).

[I1,I2,I3,...,In] = IND2SUB(SIZ,IND) returns N subscript arrays

I1,I2,..,In containing the equivalent N-D array subscripts

equivalent to IND for an array of size SIZ.

Class support for input IND:

float: double, single

See also sub2ind, find.

 

FIND Find indices of nonzero elements.

I = FIND(X) returns the linear indices corresponding to

the nonzero entries of the array X. X may be a logical expression.

Use IND2SUB(SIZE(X),I) to calculate multiple subscripts from

the linear indices I.

I = FIND(X,K) returns at most the first K indices corresponding to

the nonzero entries of the array X. K must be a positive integer,

but can be of any numeric type.

I = FIND(X,K,'first') is the same as I = FIND(X,K).

I = FIND(X,K,'last') returns at most the last K indices corresponding

to the nonzero entries of the array X.

[I,J] = FIND(X,...) returns the row and column indices instead of

linear indices into X. This syntax is especially useful when working

with sparse matrices. If X is an N-dimensional array where N > 2, then

J is a linear index over the N-1 trailing dimensions of X.

[I,J,V] = FIND(X,...) also returns a vector V containing the values

that correspond to the row and column indices I and J.

Example:

A = magic(3)

find(A > 5)

finds the linear indices of the 4 entries of the matrix A that are

greater than 5.

[rows,cols,vals] = find(speye(5))

finds the row and column indices and nonzero values of the 5-by-5

sparse identity matrix.

See also sparse, ind2sub, relop, nonzeros.

Overloaded methods:

codistributed/find

 

SUB2IND Linear index from multiple subscripts.

SUB2IND is used to determine the equivalent single index

corresponding to a given set of subscript values.

IND = SUB2IND(SIZ,I,J) returns the linear index equivalent to the

row and column subscripts in the arrays I and J for a matrix of

size SIZ.

IND = SUB2IND(SIZ,I1,I2,...,IN) returns the linear index

equivalent to the N subscripts in the arrays I1,I2,...,IN for an

array of size SIZ.

I1,I2,...,IN must have the same size, and IND will have the same size

as I1,I2,...,IN. For an array A, if IND = SUB2IND(SIZE(A),I1,...,IN)),

then A(IND(k))=A(I1(k),...,IN(k)) for all k.

Class support for inputs I,J:

float: double, single

See also ind2sub.

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