Printing positive numbers backwards

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!

[Stephen23]

Please show us what you have tried so far.

You would have made significant progress on this by doing the introductory tutorials:

https://www.mathworks.com/help/matlab/getting-started-with-matlab.html

Answer 1

[Rajani Mishra]

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 

[Stephen23]

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:

https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html

It is much simpler to just use efficient logical indexing (this gives the same output):

B = mt.';
flipud(B(B>0))