MATLAB: When I run the function I want a row vector not a column

column row transpose functionMATLAB

I have a simple function that generates large numbers. The ans is a column vector but I want a row. ans' changes it to what I want but I need it to run in the function. I'm not sure how to do that?

Best Answer

One simple solution is to use subscript indexing (but this will be quite inefficient):

function n = num(k)
n(1,1) = 1;
n(2,1) = 1;
k = 3;
while k<=100
    n(k,1) = n(k-1)+n(k-2);
    k = k+1;
end

The best solution is to preallocate the output array (much more efficient):

function n = num(k)
n = ones(100,1); % preallocate
k = 3;
while k<=numel(n)
    n(k) = n(k-1)+n(k-2);
    k = k+1;
end

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MATLAB: Making a matlab GUI. Display all values taken from an iterative loop on a static Text

k = 15;  
n = 1;
i = 0;
allK = [];
while k > n
  if mod(k, 2) == 0  % Not "mood"!
    k = k / 2;
  else
    k = (k * 3) + 1;
  end
  i       = i + 1;
  allK(i) = k;     % A warning will appear in the editor
end 
set(handles.mytext, 'String', sprintf('%d\n', allK));

Now allK grows iteratively. This is very expensive if the resulting array is large, e.g. for 1e6 elements. For your problem, the delay is negligible. A pre-allocation is not trivial here, because you cannot know how many elements are created by this function. But it is better to pre-allocate with a poor too large estimation:

allK = zeros(1, 1e6);   % instead of: allK = [];
set(handles.mytext, 'String', sprintf('%d\n', allK(1:i)));

Alternatively you can assign a cell string to the 'String' property also instead of inserting line breaks:

set(handles.mytext, 'String', sprintfc('%d', allK(1:i)));

MATLAB: Setting up vector function

In your for loop, you are using k(k1+1). if k1 is the last element of k, then k(k1+1) will be exceeding the dimension of k. If you dont care about the last term, use

 for k1 = 1:n-1
     ... Stuff ...
 end
 d(n) = k(n);

or if you need the other vectors to go to n, stick it in a conditional

 for k1 = 1:n
     ... Other Stuff ...
     if k1~=n
         d = (k(k1)+k(k1+1))*ones(n,1);
     end
 end

Best Answer

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MATLAB: Making a matlab GUI. Display all values taken from an iterative loop on a static Text

MATLAB: Setting up vector function

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