Horizontal line common to 2 graphs

I have two graphs in two different figures. Is it possible to have them side by side in the same figure with a horizontal line going from one to the other? (hard to explain in words; it's meant to be like the green line in the attached figure)

    clc;
    close all;
    clear all;

    n1 = 3;
    x = linspace(0,25,n1);
    y = 100 - 4*x;
    x2 = linspace(0,40,n1);
    y2 = 100 - 2.5*x2;

    s1 = linspace(0,4,n1);
    s2 = 4.*ones(1,n1);
    s3 = linspace(4,5,n1);
    s = cat(2,s1,s2,s3);
    xs1 = zeros(1,n1);
    xs2 = linspace(0,25,n1);
    xs3 = 25.*ones(1,n1);
    xs = cat(2,xs1,xs2,xs3);
    dt = 25.*ones(1,n1);
    dx=linspace(12.5,25,n1);
    dy=-(dx-22.5)/2.5;
    dt11 = 12.5.*ones(1,n1);

    s21 = linspace(0,2.5,n1);
    s22 = 2.5.*ones(1,n1);
    s23 = linspace(2.5,5,n1);
    s2 = cat(2,s21,s22,s23);
    xs21 = zeros(1,n1);
    xs22 = linspace(0,40,n1);
    xs23 = 40.*ones(1,n1);
    xs2 = cat(2,xs21,xs22,xs23);
    dt2 = 40.*ones(1,n1);
    dx2=linspace(24,32,n1);
    dy2=(dx2-19)/2;
    dt22 = 24.*ones(1,n1);

    xlb=0;
    xub=45;
    xubtick=25;
    figure('name','figure 1','number','off');
    set(gcf,'units','inches','renderer', 'painters');
    pos = get(gcf,'pos');
    set(gcf,'Units','inches',...
        'Position',[pos(1) pos(2) 2.8 2]);
    plot(xs,s,'Color','red');
    xlabel('quantity flow')
    ylabel('$\bigl.\frac{L_l}{L_w}\bigr.$','Interpreter','latex','rot',0)
    set(gca,...
        'Units','normalized',...
        'FontUnits','points',...
        'FontWeight','normal',...
        'FontSize',9,...
        'FontName','Times',...
        'XLim',[xlb xub],...
        'XTick',[0,12.5,25],...
        'YTick',0:1:4,...
        'YLim',[0 5],...
        'Box','off')
    set(gca, 'Position', get(gca, 'OuterPosition') - ...
        get(gca, 'TightInset') * [-1 0 1 0; 0 -1 0 1; 0 0 1 0; 0 0 0 1]);
    hold on;
    plot(dx,dy,'Color','blue');
    hleg1 = legend('curve 1','curve 2');
    legend('Location','best');
    plot(dt,s1,':','color',[.75 .75 .75]);
    plot(dt11,s1,':','color',[.75 .75 .75]);
    hold off;

    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    xlb=0;
    xub=45;
    xubtick=40;
    figure('name','figure 2','number','off');
    set(gcf,'units','inches','renderer', 'painters');
    pos = get(gcf,'pos');
    set(gcf,'Units','inches',...
        'Position',[pos(1) pos(2) 2.8 2]);
    plot(xs2,s2,'Color','red');
    xlabel('quantity flow')
    ylabel('$\bigl.\frac{L_l}{L_w}\bigr.$','Interpreter','latex','rot',0)
    set(gca,...
        'Units','normalized',...
        'FontUnits','points',...
        'FontWeight','normal',...
        'FontSize',9,...
        'FontName','Times',...
        'XLim',[xlb xub],...
        'XTick',[0,24,40],...
        'YTick',[0,1,2.5,4],...
        'YLim',[0 5],...
        'Box','off')
    set(gca, 'Position', get(gca, 'OuterPosition') - ...
        get(gca, 'TightInset') * [-1 0 1 0; 0 -1 0 1; 0 0 1 0; 0 0 0 1]);
    hold on;
    plot(dx2,dy2,'Color','blue');
    hleg1 = legend('curve 1','curve 2');
    legend('Location','best');
    plot(dt2,s21,':','color',[.75 .75 .75]);
    plot(dt22,s21,':','color',[.75 .75 .75]);
    hold off;

Answer 1

[Walter Roberson]

It is not possible to have a line between two figures. In MATLAB, "figure" refers to windows.

It is possible to have a line between two axes in a single figure.

The easiest way to do that is to create a third axes, set the axes 'visible' off (so you do not see the labels and so on), set the axes background color to 'none', and have the position overlap the two existing axes and then draw the line.

A