my code continuously showing undefined variable or function

hello everyone. I am trying to run a code but it's giving me error saying 'undefined variable or function X1' and sometimes it says 'undefined variable and function X2'. i am attaching the code below. Please help me on this.

clc;clear all;close all
s=600;
V = VideoReader('2.mp4');
Is=read(V,[1 s]);
r=240;c=320;
r1=round(r*0.4);r2=round(r*0.94);
ch=160;
ri=r2-r1;
for i=1:2:s
    tic
    C=Is(:,:,:,i);
    CI=C(r1:r2,:,:);%»®·Ö%»®·Ö
    G=rgb2gray(CI);%±ä»Ò
    %%Ñ°ÕÒãÐÖµ
    g=G(:);
    mu=mean(g);
    g=single(g);sige=std(g);%±ê×¼²î
    %ãÐÖµ
    T=mu+3*sige;
    %Ä£°åB
    B=G>T;    
    t=0;
    for u=1:ri
        for v=ch:-1:1
            if B(u,v)
                t=t+1;
                Y1=u+r1;
                X1=v;
                break
            end
        end
    end
    t=0;
    for u=1:ri
        for v=ch:c
            if B(u,v)
                t=t+1;
                Y2=u+r1;
                X2=v;
                break
            end
        end
    end
    p1=polyfit(X1,Y1,1);
    p2=polyfit(X2,Y2,1);
    x1=1:10:ch;x2=ch:10:c;
    F1=x1.*p1(1)+p1(2);
    F2=x2.*p2(1)+p2(2);
    toc
    figure(1),imshow(C),hold on
    plot(x1',F1,'g',x2',F2,'g','LineWidth',2)
    title(i)
    hold off
    mov(i)=getframe(gca);
end
movie2avi(mov,'F1´¦Àíºó');

Answer 1

[Rik]

There are two main problems with the loops you have set up: you run the risk of not defining your variables (which is causing your errors) and they are very inefficient.

Replace this

t=0;
for u=1:ri
    for v=ch:-1:1
        if B(u,v)
            t=t+1;
            Y1=u+r1;
            X1=v;
            break
        end
    end
end
t=0;
for u=1:ri
    for v=ch:c
        if B(u,v)
            t=t+1;
            Y2=u+r1;
            X2=v;
            break
        end
    end
end

with this

[u,v]=deal(1:r1,ch:-1:1);
[u_ind,v_ind]=find(B(u,v))
if ~isempty(u_ind)
    [u_ind,v_ind]=deal(u_ind(end),v_ind(end));
    Y1=u(u_ind)+r1;
    X1=v(v_ind);
else
    %prevent Y1 from not being defined
    Y1=0;X1=0;
end
[u,v]=deal(1:r1,ch:c);
[u_ind,v_ind]=find(B(u,v))
if ~isempty(u_ind)
    [u_ind,v_ind]=deal(u_ind(end),v_ind(end));
    Y2=u(u_ind)+r1;
    X2=v(v_ind);
else
    %prevent Y2 from not being defined
    Y2=0;X2=0;
end

[Shahrin Islam]

Thank you so much for your help. my code is working now. but i am facing another problem. The two lines that are supposed to align with the road marking has shifted from the desired position. I am attaching the video for your convenience. I will highly appreciate you support.

[Rik]

There is a small difference between my code and your loops:

A=false(5,5);
A(2,4)=true;A(4,2)=true;
[u,v]=find(A,1);

That returns u=4,v=2 in my code, and u=2,v=4 in your loops. I'll edit my code to fix this. This difference might be causing your issue. I have no clue what you are trying to do, so I can't help you with other bugs in you code. It also doesn't help that your code has few comments and the comment that are in there are unreadable for me.

[Shahrin Islam]

Thank you so much for the help. My code is to detect lanes marking in the road. But now it can't detect the lane anymore. The two lines that were about to show the lane have moved. Please help me if you can. Thanks in advance.

[Rik]

My updated code has the same functionality as your code, except for the case where they would be undefined. You will have to think about what value they should have in case the code that replaced the double loop fails.

[Shahrin Islam]

thank you..i will try to fix that.