MATLAB: How to plot diagonal lines starting at the last line’s end point

Question

Hello, I want to plot these red lines between each blue line, like the one all the way at the bottom but all the way up (like the red diagonals connecting the blue lines in the second picture). Any help appreciated!

img = double(mat2gray(imread('071318.bmp')));
mask_size=[5 5];
sigma=4;
Gaussian_filter = fspecial('gaussian',mask_size,sigma);
A=conv2(img, Gaussian_filter, 'same');
Gx = [-1, 0, 1; -2, 0, 2; -1, 0, 1];
Gy = [1, 2, 1; 0, 0, 0; -1, -2, -1];
SobelX = conv2(A, Gx, 'same');
SobelY = conv2(A, Gy, 'same');
gradient_direction = (atan2(SobelY, SobelX))*180/pi;
gradient_magnitude = sqrt((SobelX.^2) + (SobelY.^2));
Threshold_High = min(min(gradient_magnitude))+max(max(gradient_magnitude))*.09;
Threshold_Low = Threshold_High/2;
rows=size(A,1);
columns=size(A,2);
for i=1:rows
    for j=1:columns
        if (gradient_direction(i,j)<0) 
            gradient_direction(i,j)=360+gradient_direction(i,j);
        end
    end
end
edge_direction=zeros(rows,columns);
for i = 1  : rows
    for j = 1 : columns
        if ((gradient_direction(i,j)>=0)&&(gradient_direction(i,j)<22.5)||(gradient_direction(i,j)>=157.5)&&(gradient_direction(i,j)<202.5)||(gradient_direction(i,j)>=337.5)&&(gradient_direction(i,j)<=360))
            edge_direction(i,j)=0;
        elseif((gradient_direction(i,j)>=22.5)&&(gradient_direction(i,j)<67.5)||(gradient_direction(i,j)>=202.5)&&(gradient_direction(i,j)< 247.5))
            edge_direction(i,j)=45;
        elseif((gradient_direction(i,j)>=67.5&&gradient_direction(i,j)<112.5)||(gradient_direction(i,j)>=247.5&&gradient_direction(i,j)<292.5))
            edge_direction(i,j)=90;
        elseif((gradient_direction(i,j)>=112.5&&gradient_direction(i,j)<157.5)||(gradient_direction(i,j)>=292.5&&gradient_direction(i,j)<337.5))
            edge_direction(i,j)=135;
        end
    end
end
edge1 = zeros (rows, columns);
for i=2:rows-1
    for j=2:columns-1
        if (edge_direction(i,j)==0)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i,j+1),gradient_magnitude(i,j-1)]));
        elseif (edge_direction(i,j)==45)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i+1,j-1),gradient_magnitude(i-1,j+1)]));
        elseif (edge_direction(i,j)==90)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i+1,j),gradient_magnitude(i-1,j)]));
        elseif (edge_direction(i,j)==135)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i+1,j+1),gradient_magnitude(i-1,j-1)]));
        end
    end
end
edge2 = edge1.*gradient_magnitude;
Threshold_Low = Threshold_Low * max(max(edge2));
Threshold_High = Threshold_High * max(max(edge2));
edge_binary = zeros (rows, columns);
for i = 1  : rows
    for j = 1 : columns
        if (edge2(i, j) < Threshold_Low)
            edge_binary(i, j) = 0;
        elseif (edge2(i, j) > Threshold_High)
            edge_binary(i, j) = 1;
        elseif(edge2(i+1,j)>Threshold_High||edge2(i-1,j)>Threshold_High||edge2(i,j+1)>Threshold_High||edge2(i,j-1)>Threshold_High||edge2(i-1,j-1)>Threshold_High||edge2(i-1,j+1)>Threshold_High||edge2(i+1,j+1)>Threshold_High||edge2(i+1,j-1)>Threshold_High)
            edge_binary(i,j)=1;
        end
    end
end
edge = (edge_binary.*255);
edge(1600:2054,:)=[];
edge(:,1:300)=[];
edge=flipud(edge);
[y,x]= find(edge==255);
T= table(x,y,'VariableNames',{'x','y'}); %table of (x,y) points of bubble edge
x0=mean(x(y==min(T.y)));
T(T.x>x0,:)=[];
hold on
axis equal
title('Captive Bubble Air-Liquid Interface')
xlabel('x')
ylabel('y')
e=contour(edge,'k');
y_axis=xline(x0);
for n=0:50:max(y) %delta y small
m=min(y); %starting y value of R lines at lowest bubble edge point
x1=x(y==m+n);
delete=x1>x0;
x1(delete)=[];
x1=mean(x1);
plot([x0 x1],[m+n m+n],'b'); %R line
R=x0-x1;
    for o=m:100:max(y) %delta y big
        plot([x0 x1],[m m+n],'r');
     end
end

Answer 1

Here is what i achieved

Am i succeeded?