MATLAB: What is matrix3d

matrix3d

my code is neighbors = matrix3d(i-1:i+1, j-1:j+1, k-1:k+1);

It gives error like,

Undefined function or variable 'matrix3d'.

Best Answer

matrix3D is the variable 3D matrix you have. You have not defined it.

matrix3d = rand(10,10,10) ;
% say i = 1, j = 1
i = 2 ; j=3, k = 2
neighbors = matrix3d(i-1:i+1, j-1:j+1, k-1:k+1)

Related Solutions

MATLAB: How to find 26 neighbors of point with coordinates of (i,j,k)

To get a 27 element cube around the voxel, do this:

neighbors = matrix3d(i-1:i+1, j-1:j+1, k-1:k+1);

Then turn it into a column vector like this:

neighbors = neighbors(:);

Then delete the i,j,k element to get the final 26 neighbors, by deleting the middle element of the column vector:

neighbors[14] = [];  % Now we're done!  We have a list of 26 voxel values.

MATLAB: Fill NaN cell with mean of eight surrounding cells in grid data in matlab

If you want to replace a scalar based on a 3D array, you either need 3 nanmean calls:

nanmean(nanmean(nanmean(data(i-1:i+1, j-1:j+1, k-1:k+1))))

with i-1:i+1, instead of i-2:i+2. This would be easier:

if isnan(data(i,j,k))   % "== 1" is not needed
  tmp         = data(i-1:i+1, j-1:j+1, k-1:k+1);  % 3D block
  data(i,j,k) = nanmean(tmp(:));                  % Make it a vector
end

But this is a 3x3x3 neighborhood with 27 elements, not 8. I assume you mean:

if isnan(data(i,j,k))   % "== 1" is not needed
  tmp1        = data(i-1:i+1, j, k);
  tmp2        = data(i:i, j-1:j+1, k);
  tmp3        = data(i, j, k-1:k+1);
  tmp         = [tmp1(:); tmp2(:); tmp3(:)];  % Create a vector
  data(i,j,k) = nanmean(tmp);
end

Because the center point data(i,j,k) is included 3 times, but ignored by nanmean, you have 6 neighbors now, not 8.

So please explain again, what you exactly want.

Best Answer

Related Solutions

MATLAB: How to find 26 neighbors of point with coordinates of (i,j,k)

MATLAB: Fill NaN cell with mean of eight surrounding cells in grid data in matlab

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