Printing positive numbers backwards

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David Tejcek
David Tejcek on 2 Jul 2019
Edited: Stephen23 on 16 Jul 2019
Hi all,
I was just wondering if anyone could help me out with some code to go through a matrix of numbers and find the positive numbers and print only them (remove the negative numbers) in a new array but also print them in reverse order,
Thanks a lot!
  1 Comment
Stephen23
Stephen23 on 2 Jul 2019
Edited: Stephen23 on 2 Jul 2019
Please show us what you have tried so far.
You would have made significant progress on this by doing the introductory tutorials:

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Answers (1)

Rajani Mishra
Rajani Mishra on 16 Jul 2019
Hi,
I understand that you want to extract positive numbers from matrix and store them in a new array and then traverse the new array in reverse order.
Refer this code:
[row,col] = size(mt)
arr = [];
for i = 1:row
for j = 1:col
if mt(i,j) > 0
arr(numel(arr) + 1) = mt(i,j);
end
end
end
for i = numel(arr):-1:1
disp(arr(i));
end
  1 Comment
Stephen23
Stephen23 on 16 Jul 2019
Edited: Stephen23 on 16 Jul 2019
Is there are reason why this answer does not use MATLAB's basic (and most useful) features, e.g. logical indexing, code vectorization, etc.?
Note that the output array should be preallocated:
It is much simpler to just use efficient logical indexing (this gives the same output):
B = mt.';
flipud(B(B>0))

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