I keep getting 'Error using + Matrix dimensions must agree' how do i fix this?

The code it keeps doing it for is

V=V+k*q(i).r;

[José-Luis]

Have you tried using the debugger and looking at the sizes of the different variables?

[Zoltán Csáti]

Paste a larger chunk of code to see what is wrong.

[Adam]

We have no idea what V, k, q, i and r are. Clearly their details are key to solving this problem!