what is error actually in my code, any one solve this?

 xdim=50;
ydim=50;
v_now=zeros(xdim,ydim);
v_prev=zeros(xdim,ydim);
for i=1:1:ydim
v_now(i,xdim)=20;
end
x=0.01;
for k=[0.01,0.001,0.0001,0.00001]
iter=0;
iter_error=max(max(abs(v_now-v_prev)));
while(iter_error>k)
    iter=iter+1;
    for i= 2:1:xdim-1
        for j=2:1:ydim-1       
            v_now(i,j)=(v_now(i-1,j)+v_now(i+1,j)+v_now(i,j-1)+v_now(i,j+1))/4;
        end
    end
    iter_error=max(max(abs(v_now-v_prev)));
    v_prev=v_now;
end
 h(k)=iter;
end
plot(k,h(k));

Answer 1

[Julia]

Your problem is that k is not an integer. Matlab considers h as an array and you must use integers to access the entries of arrays.

Answer 2

[Hikaru]

A for loop will repeat a statement for a specified number of times. The line

for k=[0.01,0.001,0.0001,0.00001]

should be fixed. You can use decimal as increments in for loop, but for indexing, you need to use other variables.

h(k)=iter; %the elements in k are not integers, so you cannot use them as index.

[Julia]

But you can use a for-loop in this fashion. The error that occurs is because of h(k).

[Dhines]

i modified it.. but the graph comes blank

[Hikaru]

Thanks Julia, I edited my statement to make it clearer. I meant to say it's not okay for indexing.

OP, can you update the modified code? We can try to see where the problem is.