MATLAB: How make matrix from a for loop

for loop

My code like this,
……….. …………
x_error=zeros(1,1);
y_error=zeros(1,1);
z_error=zeros(1,1);
lz=1.5; %lx=1.35; %ly=1.4;
for i=1:1:5 ly=i;
    for j=1:1:5;
       lx=j;
   ......................
    X=abs(x(1,1));
    Y=abs(x(1,2));
    H=abs(x(1,3));
    x_error(i,j)=abs(X-lx);
    y_error(i,j)=abs(Y-ly);
    z_error(i,j)=abs(abs(z1-H)-lz);
    end
end 
x_er=x_error
y_er=y_error
z_er=z_error
it's work but when i change i=1:1:5 to i=1:0.1:5 and j=1:1:5; to j=1:0.1:5;
then error like this >>Attempted to access x_error(1.1,1); index must be a positive integer or logical.
how can i solve this i need to get the x_error value in matrix form not in a cell array form

Best Answer

Since the two for loops now iterate with a step size of 0.1, then i and j are no longer positive integer values (1,2,3,4,5, etc.) and so accessing the arrays will fail with the ..index must be a positive integer or logical error message for rational values like 1.1,1.2,1.3,etc.
To accommodate this, you could do the following: realize that the number of elements in 1:0.1:5 is just 41 (try length(1:0.1:5)), pre-allocate memory to your matrices, and use local variables to act as your step sizes:
 n = length(1:0.1:5);
 % pre-allocate memory to the error arrays
 x_error = zeros(n,n);
 y_error = zeros(n,n);
 z_error = zeros(n,n);
 % initialize the step sizes
 lx = 1;
 ly = 1;
 % loop
 for i=1:n
   % re-initialize lx to be one  ---> new code!
   lx = 1;
   for j=1:n
     % do stuff
     % set the errors
     x_error(i,j)=abs(X-lx);
     y_error(i,j)=abs(Y-ly);
     z_error(i,j)=abs(abs(z1-H)-lz);
     % increment lx  ---> new code!
     lx = lx + 0.1;
   end
   % increment ly    ---> new code!
   ly = ly + 0.1;
 end
This way, the code will always be using positive integers to access the error arrays. Try the above and see if it helps!
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