How to remove rows in a multidimensional matrix?
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I have a three dimensional matrix (A) and I want to remove rows that contain 0. I tried to do this in a 'for loop', but it gives an error "A null assignment can have only one non-colon index.". When I replace [] with NaN, it seems the code and index are right. Does it possible to do this outside of 'for loop'? Thank you in advance for your help.
clear all
clc
A1 = [50, 1, 130; 50, 1, 140; 0, 0, 0; 0, 0, 0];
A2 = [0, 0, 0; 51, 2, 131; 51, 2, 141; 0, 0, 0];
A3 = [0, 0, 0; 0, 0, 0; 52, 3, 132; 52, 3, 142];
A (:,:,1)= A1;
A (:,:,2) = A2;
A (:,:,3) = A3;
disp (A)
[r,c] = size(A);
for i = 1:3
for h = 1:r
if A (h,:,i) == 0
A (h,:,i) = [] ; % = NaN
end
end
end
disp(A)
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Thorsten
il 19 Lug 2015
for k=1:size(A,3)
Ak = A(:,:,k);
B(:,:,k)= Ak(sum(Ak')~=0,:);
end
2 Commenti
Image Analyst
il 20 Lug 2015
Then you will have to store your data in a cell array like John said. A cell array must be rectangular like any other array, but the contents of the cells can be of different sizes which, in effect, will allow you to do this complicated thing you want to do. See the FAQ: http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F
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Image Analyst
il 19 Lug 2015
A "row" is really a plane. For example row 2 will occur for every value of column and slice, so it's really a plane. That is A(2, :, :) is a plane along the x-z plane. To get rid of "row" 2, use []:
A(2, :, :) = [];
Any element which would have appeared with 2 as the first index (the "row" index) will now be gone.
5 Commenti
John D'Errico
il 19 Lug 2015
And my comment is you CANNOT delete one row from the first plane, and NOT from the second plane!!!!!!! Trying to do so would have the effect of creating a non-rectangular matrix.
If you absolutely need to do this, then you need to consider a different structure for your data storage. Perhaps use a cell array of rectangular matrices, which can then be different sizes. Any sizes at all in fact.
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