在Matlab中重塑后查找元素w.r.t原始矩阵的位置

Question

我有一个 1*262144 矩阵，我已将其重新整形为 512*512 矩阵。现在，我需要第二个矩阵中的某些元素，并且想知道它们在原始行矩阵中的位置。说，我需要在我的重塑矩阵中位于 (256,4) 的元素。我怎样才能知道这个元素在我原来的仅行矩阵中的位置？

 matri_working_now = C(1,:);
    matrix_working_now = reshape(matri_working_now,512,512);
    [nrows,ncols] = size(matrix_stables);   %matrix_stables is a matrix over which I am looping over which contains the locations of the desired elements as per the reshaped matrix. this itself is a 30839*2 matrix
    for row = 1:nrows
        for col = 1:ncols
        %sub2ind(size(matrix_working_now),row,col)
        %fprintf('iteration is equal to %6.2f.\n',row,col);
        [rowss colum] = ind2sub(size(matri_working_now),sub2ind(size(matrix_working_now),matrix_stable(row),matrix_stable(col)));    % i am accessing the elements of matrix_stables which provide me the row and column numbers; 

        end
    end

有什么建议/想法吗？

谢谢！

Answer 1

由于你的原始矩阵是一个向量，你只需要convert from subindices to linear index，sub2ind：

col = sub2ind(size(reshapedMatrix), 256,4);

一般来说，如果原始矩阵不一定是向量，则需要第二步用ind2sub：

[row col] = ind2sub(size(originalMatrix), sub2ind(size(reshapedMatrix), 256,4));

例子：

>> originalMatrix = (1:10).^2
originalMatrix =
     1     4     9    16    25    36    49    64    81   100

>> reshapedMatrix = reshape(originalMatrix, 2,5)
reshapedMatrix =
     1     9    25    49    81
     4    16    36    64   100

>> reshapedMatrix(2,3)
ans =
    36

>> [row col] = ind2sub(size(originalMatrix), sub2ind(size(reshapedMatrix), 2,3))
row =
     1
col =
     6

>> originalMatrix(row,col)
ans =
    36