Error: subscript indices must be either positive integers or logicals

This is my histogram function(histIntensity) with parameters M as a random image matrix and N as the maximal number of Bits

function vector = histIntensity(M,N)
  x=rows(M);
  y=columns(M);
  vector=zeros(1,N);

  for i=1:x
    for j=1:y
      if(M(i,j)<(N+1))
      vector(M(i,j))++;
    end
       end    
         end
endfunction

And this is an image matrix (255x255) with vertical intensity variation:

T=zeros(255,255);
x=0:pi/254:pi;
y=sin(x/2);
plot(x,y);
T(:,:)=repmat(y,255,1); 
imshow(T')

b=histIntensity(T,2^8)
bar(b)

But when i try to "call up" my histogram function it shows this error:

error: index (0): subscripts must be either integers 1 to (2^31)-1 or logicals

Could someone please tell me where is the mistake and what should i change?

Thank you :)

[Star Strider]

This appears to be Octave code.

What line or call is throwing the error?

[David Hill]

function vector = histIntensity(M,N)
  x=rows(M);
  y=columns(M);
  vector=zeros(1,N);
  for i=1:x
    for j=1:y
      if(M(i,j)<(N+1))
      vector(M(i,j))++;%M(i,j) does not have to be an integer, you cannot index using it. What are you trying
      %to do here? Also matlab does not recognize ++.
      end
    end    
  end
end

[Kristi Mako]

The code is in Octave

vector(M(i,j))++ %here calculates every value of the histogram

I think the mistake could be in this code:

T=zeros(255,255);
x=0:pi/254:pi;
y=sin(x/2);
plot(x,y);
T(:,:)=repmat(y,255,1); 
imshow(T')

Answer 1

[Image Analyst]

See the FAQ: https://matlab.fandom.com/wiki/FAQ#How_do_I_fix_the_error_.22Subscript_indices_must_either_be_real_positive_integers_or_logicals..22.3F

In MATLAB, the code would be:

x=0:pi/254:pi;
y=sin(x/2);
plot(x,y);
T=repmat(y, [255,1]); 
imshow(T);
axis('on', 'image');
xlabel('x', 'FontSize', 20);
ylabel('y', 'FontSize', 20);