How to plot two types of marking in one single line continuously?

I am trying to make a plot of different types of marks along a line generated by using ginput.

Let's say I have a line and there are a series of point generated by the ginput with a constant increment in x, shown as attached figure1. The position vectors are

X=[ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22]

Then I have 2 set of position vectors that seperated from X which are

x1=[1 2 3 4 5 6 11 12 13 14 18 19 20 21] , x2=[7 8 9 10 15 16 17]

for the points in x1 I need to plot dash line and x2 i need plot straight line. The result can illustrated in figure2.

My code is as below. I have tried using X(end) and X(1) but what I hope is it can refer back the previous value such as the 7th x value in x2 should refer to the 6th x value in x1 by knowing the increment. The increment is not fix as 1, it just an example.

Anyone have idea about these?

axis([0 22 0 22]);
hold on

S = ginput(2);
Sx = round(S(1,1));
Sy = round(S(1,2));
Ex = round(S(2,1));
Ey = round(S(2,2));

m =(Ey-Sy)/(Ex-Sx);
c = Ey-m*(Ex);

if Ex>Sx
        x = Sx:1:Ex;
        y = round(m*x+c);
        plot(x,y,'*','Color','b', 'MarkerSize',5);  
        
   elseif Ex<Sx
        x = Sx:-1:Ex;
        y = round(m*x+c);
        plot(x,y,'*','Color','b', 'MarkerSize',5); 
end

plot([Sx Ex],[Sy Ey],'x','Color','r', 'MarkerSize',10);
hold on

Answer 1

[darova]

Look

axis([0 22 0 22]);
ind = [1 2 3 4 5 6   11 12 13 14   18 19 20 21 22]; 
S = ginput(2);
n = ind(end);
x = linspace(S(1,1),S(2,1), n);
y = linspace(S(1,2),S(2,2), n);
cla
hold on
plot(x,y,'.b')

for i = 1:length(ind)-1
    i1 = ind(i);
    i2 = ind(i+1);
    if (i2-i1 == 1) && mod(i1,2) 
        plot([x(i1) x(i2)], [y(i1) y(i2)], '-k')
    elseif i2-i1 > 1
        plot([x(i1+1) x(i2-1)], [y(i1+1) y(i2-1)], '-r')
    end
end

plot([x(1) x(end)], [y(1) y(end)], 'xr','MarkerSize',10)
hold on

But dont know about this

[Josh Hwa]

I think its because of using (end) but it worked. Thank you so much!