Subscripted assignment dimension mismatch

Can anyone highlight why i am getting this error in the below code please?

domainSize = [50 50];
domain = zeros(domainSize);
domain(24:26,24:26) = 1;

% Generate Position Arrays
[particlePosition(:,1), particlePosition(:,2)] =find(domain);

for i = 1:length(particlePosition)
    %Select Direction to Move
    switch ceil(4 * rand)
        case 1
            dR = [-1 0];
        case 2
            dR = [+1 0];
        case 3
            dR = [0 -1];
        case 4
            dR = [0 +1];
    end

      %New Particle Location
      tempPosition = particlePosition + dR;

      %Move Particle
      particlePosition(i,:) = tempPosition;

end

Answer 1

[Roger Stafford]

There are quite a few things wrong with this code.

1) In “for i = 1:length(particlePosition)” you will get only three values of i from 1 to 3, but you have nine “particles” to move.

2) The part of the code that begins with “%New Particle Location” is located outside the for-loop so only the last “particle” is moved.

3) The line “tempPosition = particlePosition + dR;” attempts to add ‘particlePosition’, which is a 9 x 2 matrix to ‘dR’, which is only a 1 x 2 vector. Naturally Matlab will object strenuously to such an ill-advised attempt. This is undoubtedly the source of your error message.

[Walter Roberson]

Note: since R2016b, adding a 9 x 2 and a 1 x 2 will work, and will be the same as if you had use bsxfun() to do the addition.

[Shane McNamara]

Thanks for your help :D