parfor shows an empty figure

Hello,

I am trying to use parfor to plot some filled rectangles with the following codes for some data x,y,f and a parameter l, this code works fine on serial for loop, when I tried to do it with parfor, it returns an empty figure, how should I resolve this? Thank you!

figure();
for i = 1:length(f)
   
    if f(i)==1
       
        fill( [x(i) x(i)+l x(i)+l x(i)],...
              [y(i) y(i) y(i)+l y(i)+l],[0 91 187]/255,'LineStyle','none');hold on;
        
    end
    
end

[Adam]

I don't think plotting instructions are supported by parallel processing, though I may be wrong.

[J T]

I have used similar codes previously to plot scattered data points, so I believe it does support, or at least in the lastest versions.

[Adam Danz]

Could it be that l (bad variable name) is equal to 0? In that case, the patch produced by fill() would have an area of 0 (not visible).

[J T]

l is not zero, is a fixed positive length for all data points, note that the exact same code works in serial, it is just taking forever. Btw, why is l a bad variable name?

[Adam Danz]

" Btw, why is l a bad variable name"

• l looks like 1. When a human is reading your code, it's very easy to misinterpret y(i)+l as adding 1
• Single character variable names are often used in loops (for i = 1:10) and to represent common variables such as p-values (p = anova1(...)) but in general, it's best to use variable names with more than 1 character.
• When using the editor, if you select a variable you'll notice that all instances of that variable within the same function are highlighted. With a variable name as narrow as l you lose the ability to quickly see all of those instances.
• It's very easy to accidentally type a single-character variable name via a typo. It's much more difficult to accidentally type LValue than l.

[J T]

Thanks! Good to learn!