one program has different results in different versions

Here is the code:

C=0.3+0.5i;                               
V = linspace(-2.0,2.0,400);             
[Re,Im] = meshgrid(V);
Z = Re + i * Im;                             
B = 0;
for K = 1:100                                                
    B = B+(abs(Z)<=2);
    Z = Z.*Z + C;
end;
imagesc(B);                                          
colormap(jet);
axis equal

In 2018a, the result is:

But, in 2015b, the result is:

Why this will happen? How can I get the second figure in 2018a version? Thank you very much.

[Star Strider]

For what it’s worth, I get the R2015b result in R2019a.

[the cyclist]

I get your R2015b result with R2018b. Maybe a bug was introduced between R2015b and R2018a, which was fixed in R2018b?

[per isakson]

I get your R2015b image with both R2018a and R2018b.

[Walter Roberson]

Fractal in R2016b, R2017b, R2018a, R2018b, R2019a on Mac

Do you just happen to have an AMD cpu?

Answer 1

[Steven Lord]

In release R2018a did you assign a value to the variable i before running that code? When you want to ensure that you're using the square root of -1 you should always use 1i. Try replacing your line:

    Z = Re + i * Im;

with

Z = Re + 1i * Im;

[per isakson]

Yes adding i=1;

%%
i = 1;
C=0.3+0.5i;  
etc.

did it

on R2018b